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Physics Questions > Final > Flashcards

Final Flashcards

1
Q

A particularly scary roller coaster contains a loop-the-loop in which the car and rider and are completely upside down. If the radius of the loop is 13.2 m, with what minimum speed must the car traverse the loop so that the rider does not fall out while upside down at the top? Assume the rider is not strapped to the car.

A

11.4 m/s

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2
Q

A 0.50-kg toy is attached to the end of a 1.0-m very light string. The toy is whirled in a horizontal circular path on a frictionless tabletop. If the maximum tension that the string can withstand without breaking is 350 N. What is the maximum speed the mass can have without breaking the string?

A

26 m/s

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3
Q

Two forces produce equal torques on a door about the door hinge. The first force is applied at the midpoint of the door, the second force is applied at the doorknob. Both forces are applied perpendicular to the door. Which force has a greater magnitude?

A

The first force (at the midpoint)

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4
Q

Two planets have the same surface gravity, but planet B has twice the mass of planet A. If planet A has radius r, what is the radius of planet B?

A

r (square root of 2)

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5
Q

A wooden block contains some nails so that its density is exactly equal to that of water. If it is placed in a tank of water. If it is placed in a tank of water and released from rest when it is completely submerged, it will

A

remain where it is released.

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6
Q

A mechanic is examining the wheel of a bicycle to adjust the brake. With the bicycle off the ground, he manually rotates the wheel until it reaches an angular speed of 12.0 rad/s and then allows it to coast to a stop. If the wheel has a moment of inertia of 0.100 kg x m2, and the wheel slows uniformly to a stop in 160 s, what is the magnitude of the retarding torque?

A

0.00750 N x m

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7
Q

A pulley has an inital angular speed of 12.5 rad/s and a constant angular acceleration of 3.41 rad/s2. Through what angle does the pulley turn in 5.26 s?

A

113 rad

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8
Q

A certain gas is compressed adiabatically. The amount of work done on the gas is 800 J. What is the change in the internal (thermal) energy of the gas?

A

800 J

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9
Q

A cyclic process is carried out on an ideal gas such that it returns to its initial state at the end of the cycle, as shown in the pV diagram in the figure. If the process is carried out in a counter-clockwise sense around the enclosed area, as shown in the figure, then the magnitude of the enclosed area represents

A

the work done on the gas.

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10
Q

Find the orbital speed of an ice cube in the rings of Saturn. The mass of Saturn is 5.68 x 1026 kg, and use an orbital radius of 1.00 x 105 km.

A

19.5 km/s

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11
Q

Ideal incompressible water flows through a horizontal pipe of cross-sectional area 10.0 cm2 at a pressure of 0.250 atm with a volume flow rate of 1.00 x 10-3m3/s At a valve, the effective cross-sectional area of the pipe is reduced to 5.00 cm2. What is the pressure at the valve?

A

0.235

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12
Q

Glycerin with a viscosity of 1.5 Nxs/m2, is flowing with an average speed of 1.2 m/s through a tube that has a raduis fo 5.0 mm and is 25 cm long.

A

140 kPa

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13
Q

A large vat contains 1.000 L of water at 20 C. What volume will this water occupy when it is heated up to 80 C. Water has a volume expansion coefficient of 210 x 10 -6 K -1.

A

1.013 L

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14
Q

A blacksmith is flattening a steel plate having dimensions 10 cm x 15 cm x 1 mm. He has heated the plate to 900 K. If the emissivity of the plate is 0.75, at what rate does it lose energy by radiation? Ignore any heat exchange with the surroundings.

A

850 W

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15
Q

A gas follows the pV trajectory shown in the figure 16.2. How much work is done per cycle by the gas if the gas in a heat engine follows the cycle shown in the pV diagram. How much work does this engine do each cycle if PO = 5.4 atm?

A

220 J

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16
Q

When you blow some air above a paper strip, the paper rises. This happens because

A

the air above the paper moves faster and the pressure is lower.

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17
Q

By what primary heat transfer mechanism does the sun warm the earth?

A

radiation

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18
Q

A certain ideal gas has a molar specific heat at constant volume 7R/2. What is its molar specific heat at constant pressure?

A

9R/2

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19
Q

A 0.14-kg baseball is dropped from rest from a height of 2.0 m above the ground. What is the magnitude of its momentum just before it hits the ground if we neglect air resistance?

A

0.88 kg x m/s

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20
Q

A 1200-kg cannon suddenly fires a 100-kg cannonball at 35 m/s. What is the recoil speed of the cannon? Assume that frictional forces are neglible and the cannon is fired horizontally.

A

2.9 m/s

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21
Q

A small car meshes with a large truck in a head-on collision. Which of the following statements concerning the momentum during the collision are correct? (There could be more than one correct choice).

A

The car and the truck must undergo the same change in speed.

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22
Q

A 2.0-kg ball moving eastward at 3.0 m/s suddenly collides with and sticks to a 4.0-kg ball moving northward at 2.0 m/s. What is the magnitude of the momentum of this system just after the collision>

A

10 kg x m/s

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23
Q

An 8.0 bullet is suddenly shot into a 4.0-kg block that is at rest on a frictionless horizontal surface, as shown in the figure. The bullet remains lodged in the block. The block then moves against a spring and compresses it by 3.7 cm. The force constant (spring constant) of the spring is 2500 N/m. What was the initial speed v of the bullet?

A

460 m/s

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24
Q

A block of mass m = 34 kg and speed V is behind a block of mass M = 81 kg and speed of 0.50 m/s, as shown in the figure. The surface is frictionelss and the blocks collide and couple. After the collision, the blocks have a common speed of 0.90 m/s. What is the magnitude of the impulse on the 34-kg block due to the collision?

A

32 N x s

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25
Q

A 0.24 kg blob of clay is thrown at a wall with an initial horizontal velocity of 16 m/s. If the clay comes to a stop in 91 ms, what is the average horizontal force on the clay due to the wall?

A

42 N

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26
Q

A tiger is running in a straight line. If we double both the mass and speed of the tiger, the magnitude of its momentum will increase by what factor?

A

4

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27
Q

A rocket explodes into two fragments, one 25 times heavier than the other. The magnitude of the momentum change of the lighter fragment is

A

The same as the momentum change of the heavier fragment.

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28
Q

You are standing on a skateboard, initially at rest. A friend throws a very heavy ball towards you. You have two choices about what to do with the ball: either catch the ball or deflect it back toward your friend with the same speed as it was originally thrown. Which choice should you make in order to maximize your speed on the skateboard?

A

Deflect the ball back.

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29
Q

In the figure, determine the character of the collision. The masses of the blocks, and the velocities before and after, are shown. The collision is

A

completely inelastic

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30
Q

A very elastic rubber ball is dropped from a certain height and hits the floor with a downward speed v. Since it is so elastic, the ball bounces back with the same speed v going upward. Which of the following statements about the bounce are correct? (There could be more than one correct choice.)

A

The magnitude of the ball’s momentum was the same just before and just after the bounce.

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31
Q

In an inelastic collision involving an isolated system, the final total momentum is

A

exactly the same as the initial momentum.

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32
Q

In the figure showing an isolated system, determine the character of the collision. The masses of the blocks, and the velocities before and after, are shown. The collision is

A

not possible because momentum is not conserved.

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33
Q

Identical forces act for the same length of time on two different objects. The magnitude of the change in momentum of the lighter object is

A

exactly equal to the magnitude of the change in momentum of the larger mass.

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34
Q

A small car meshes with a large truck in a head-on collision. Which of the following statements concerning the momentum during the collision are correct? (There could be more than one correct choice.)

A

The momentum of the car-truck system is conserved, but the momentum of each one separately is not conserved.

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35
Q

A 2.0-kg ball moving eastward at 3.0 m/s suddenly collides with and sticks to a 4.0-kg ball moving northward at 2.0 m/s. What is the magnitude of the momentum of this system just after the collision?

A

10 kg ∙ m/s

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36
Q

An 8.0-g bullet is suddenly shot into a 4.0-kg block that is at rest on a frictionless horizontal surface, as shown in the figure. The bullet remains lodged in the block. The block then moves against a spring and compresses it by 3.7 cm. The force constant (spring constant) of the spring is What was the initial speed v of the bullet?

A

460 m/s

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37
Q

A block of mass m = 34 kg and speed V is behind a block of mass M = 81 kg and speed of as shown in the figure. The surface is frictionless and the blocks collide and couple. After the collision, the blocks have a common speed of What is the magnitude of the impulse on the 34-kg block due to the collision?

A

32 N x s

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38
Q

A 900-kg car traveling 30.0° south of east at 12.0 m/s suddenly collides with a 750-kg car traveling north at 17.0 m/s. The cars stick together after colliding. What is the speed of the wreckage just after the collision?

A

12.2 m/s

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39
Q

A 50-g ball moving at 10 m/s in the +x direction suddenly collides head-on with a stationary ball of mass 100 g. If the collision is perfectly elastic, what is the velocity of each ball immediately after the collision?

A

-3.3 m/s, +6.7 m/s

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40
Q

A 0.10-kg ball, traveling horizontally at 25 m/s, strikes a wall and rebounds at 19 m/s. What is the magnitude of the change in the momentum of the ball during the rebound?

A

4.4 kg ∙ m/s

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41
Q

An 8.0-g bullet is suddenly shot into a 4.0-kg block, at rest on a frictionless horizontal surface, as shown in the figure. The bullet remains lodged in the block. The block then moves against a spring and compresses it by 8.9 cm. The force constant (spring constant) of the spring is What is the magnitude of the impulse on the block (including the bullet inside) due to the spring during the entire time interval during which the block compresses the spring?

A

13 N x s

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42
Q

As shown in the figure, a bullet of mass 0.010 kg moving horizontally suddenly strikes a block of wood of mass 1.5 kg that is suspended as a pendulum. The bullet lodges in the wood, and together they swing upward a vertical distance of 0.40 m. The length of the string is 2.0 m. What was the speed of the bullet just before it struck the wooden block?

A

420 m/s

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43
Q

A 0.24 kg blob of clay is thrown at a wall with an initial horizontal velocity of If the clay comes to a stop in what is the average horizontal force on the clay due to the wall?

A

42 N

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44
Q

A 328-kg car moving at 19.1 m/s in the +x direction hits from behind a second car moving at in the same direction. If the second car has a mass of and a speed of right after the collision, what is the velocity of the first car after this sudden collision?

A

14.0 m/s

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45
Q

A 0.140-kg baseball is dropped from rest. It has a speed of 1.20 m/s just before it hits the ground, and it rebounds with an upward speed of 1.00 m/s. The ball is in contact with the ground for 0.0140 s. What is the average force exerted by the ground on the ball during the time of contact?

A

22.0 N upwards

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46
Q

You are making a circular turn in your car on a horizontal road when you hit a big patch of ice, causing the force of friction between the tires and the road to become zero. While the car is on the ice, it

A

moves along a straight-line path in its original direction.

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47
Q

When an object moves in uniform circular motion, the direction of its acceleration is

A

is directed toward the center of its circular path.

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48
Q

A car goes around a circular curve on a horizontal road at constant speed. What is the direction of the friction force on the car due to the road?

A

perpendicular to the curve inward

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49
Q

When a car goes around a circular curve on a horizontal road at constant speed, what force causes it to follow the circular path?

A

the friction force from the road.

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50
Q

Two cars go around a banked curve at the proper speed for the banking angle. One car has tires with excellent traction, while the other car has bald slippery tires. Which of these cars is more likely to slide on the pavement as it goes around the curve?

A

Neither car will slide.

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51
Q

A jet plane flying 600 m/s experiences an acceleration of 4.0 g when pulling out of a circular dive. What is the radius of curvature of the circular part of the path in which the plane is flying?

A

9200 m

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52
Q

A 0.50-kg toy is attached to the end of a 1.0-m very light string. The toy is whirled in a horizontal circular path on a frictionless tabletop. If the maximum tension that the string can withstand without breaking is 350 N. What is the maximum speed the mass can have without breaking the string?

A

26 m/s

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53
Q

A particularly scary roller coaster contains a loop-the-loop in which the car and rider are completely upside down. If the radius of the loop is with what minimum speed must the car traverse the loop so that the rider does not fall out while upside down at the top? Assume the rider is not strapped to the car.

A

11.4 m/s

54
Q

A 1000-kg car is moving at 30 m/s around a horizontal unbanked curve whose diameter is 0.20 km. What is the magnitude of the friction force required to keep the car from sliding?

A

9000 N

55
Q

A 1000-kg car is slowly picking up speed as it goes around a horizontal unbanked curve whose radius is 100 m. The coefficient of static friction between the tires and the road is 0.35. At what speed will the car begin to skid sideways?

A

19 m/s

56
Q

Two forces produce equal torques on a door about the door hinge. The first force is applied at the midpoint of the door; the second force is applied at the doorknob. Both forces are applied perpendicular to the door. Which force has a greater magnitude?

A

the first force (at the midpoint)

57
Q

Two equal-magnitude forces are applied to a door at the doorknob. The first force is applied perpendicular to the door, and the second force is applied at 30° to the plane of the door. Which force exerts the greater torque about the door hinge?

A

the first force (applied perpendicular to the door)

58
Q

Five forces act on a rod that is free to pivot at point P, as shown in the figure. Which of these forces is producing a counter-clockwise torque about point P? (There could be more than one correct choice.)

A

Force C

59
Q

There must be equal amounts of mass on both sides of the center of mass (or center of gravity) of a system.

A

False

60
Q

As shown in the figure, a given force is applied to a rod in several different ways. In which case is the torque about the pivot P due to this force the greatest?

A

1

61
Q

A pulley has an initial angular speed of 12.5 rad/s and a constant angular acceleration of 3.41 rad/s2. Through what angle does the pulley turn in 5.26 s?

A

113 rad

62
Q

How long does it take for a rotating object to speed up from 15.0 rad/s to 33.3 rad/s if it has a uniform angular acceleration of 3.45 rad/s2?

A

5.30 s

63
Q

Three small masses are positioned as follows: 2.0 kg at (0.0 m, 0.0 m), 2.0 kg at (2.0 m, 0.0 m), and 4.0 kg at (2.0 m, 1.0 m). Determine the coordinates of the center of mass (or center of gravity) of this system.

A

(1.5 m, 0.50 m)

64
Q

Three masses are located in the x-y plane as follows: a mass of 6 kg is at (0 m, 0 m), a mass of 4 kg is at (3 m, 0 m), and a mass of 2 kg is at (0 m, 3 m). Where is the center of mass (or center of gravity) of the system?

A

(1 m, 0.5 m)

65
Q

A 3.0-kg mass is located at (0.0 m, 8.0 m), and a 1.0-kg mass is located at (12 m, 0.0 m). You want to add a 4.0-kg mass so that the center of mass (or center of gravity) of the three-mass system will be at the origin. What should be the coordinates of the 4.0-kg mass?

A

(-3.0 m, -6.0 m)

66
Q

A 95-N force exerted at the end of a 0.32-m long torque wrench produces a torque of 15 N ∙ m. What is the angle (less than 90°) between the wrench handle and the direction of the applied force?

A

30

67
Q

A machinist turns on the power to a grinding wheel at time t = 0 s. The wheel accelerates uniformly from rest for 10 s and reaches the operating angular speed of The wheel is run at that angular speed for 30 s and then power is shut off. The wheel slows down uniformly at until the wheel stops. In this situation, what is the angular acceleration of the wheel between and

A

3.8 rad/s2

68
Q

A Ferris wheel rotating at 20 rad/s slows down with a constant angular acceleration of magnitude 5.0 rad/s2. How many revolutions does it make while slowing down before coming to rest?

A

6.4

69
Q

A mechanic is examining the wheel of a bicycle to adjust the brake. With the bicycle off the ground, he manually rotates the wheel until it reaches an angular speed of 12.0 rad/s and then allows it to coast to a stop. If the wheel has a moment of inertia of 0.100 kg ∙ m2, and the wheel slows uniformly to a stop in 160 s, what is the magnitude of the retarding torque?

A

0.00750 N ∙ m

70
Q

Through how many degrees does a 33 rpm turntable rotate in 0.32 s?

A

63

71
Q

Two equal-magnitude forces are applied to a door at the doorknob. The first force is applied perpendicular to the door, and the second force is applied at 30° to the plane of the door. Which force exerts the greater torque about the door hinge?

A

the first force (applied perpendicular to the door)

72
Q

The figure shows scale drawings of four objects, each of the same mass and uniform thickness, with the mass distributed uniformly. Which one has the greatest moment of inertia when rotated about an axis perpendicular to the plane of the drawing at point P?

A

B

73
Q

Five forces act on a rod that is free to pivot at point P, as shown in the figure. Which of these forces is producing a counter-clockwise torque about point P? (There could be more than one correct choice.)

A

Force C

74
Q

The rotating systems shown in the figure differ only in that the two identical movable masses are positioned a distance r from the axis of rotation (left), or a distance r/2 from the axis of rotation (right). If you release the hanging blocks simultaneously from rest,

A

the block at the right lands first.

75
Q

Two forces produce equal torques on a door about the door hinge. The first force is applied at the midpoint of the door; the second force is applied at the doorknob. Both forces are applied perpendicular to the door. Which force has a greater magnitude?

A

the first force (at the midpoint)

76
Q

The drum shown in the figure has a radius of 0.40 m and a moment of inertia of 2.3 kg ∙ m2about an axis perpendicular to it through its center. The frictional torque at the drum axle is 3.0 N ∙ m. A 14-m length of rope is wound around the rim. The drum is initially at rest. A constant force is applied to the free end of the rope until the rope is completely unwound and slips off. At that instant, the angular speed of the drum is The drum then slows down at a constant rate and comes to a halt. In this situation, what was the magnitude of the constant force applied to the rope?

A

51 N

77
Q

As shown in the figure, a 35.30-kg box is attached to a light string that is wrapped around a cylindrical frictionless spool of radius 10.0 cm and moment of inertia 4.00 kg ∙ m2. The spool is suspended from the ceiling, and the box is then released from rest a distance 3.50 m above the floor. How long does it take for the box to reach the floor?

A

2.97 s

78
Q

In a laboratory experiment, a student brings up the rotational speed of a flywheel to 30.0 rpm. She then allows it to slow down on its own, and counts 240 revolutions before the apparatus uniformly comes to a stop. The moment of inertia of the flywheel is 0.0850 kg ∙ m2. What is the magnitude of the retarding torque on the flywheel?

A

0.000278 N ∙ m

79
Q

A potter’s wheel has the shape of a solid uniform disk of mass and radius 0.65 m. It spins about an axis perpendicular to the disk at its center. A small 2.1 kg lump of very dense clay is dropped onto the wheel at a distance 0.41 m from the axis. What is the moment of inertia of the system about the axis of spin?

A

1.8 kg ∙ m2

80
Q

A uniform solid cylinder of mass 10 kg can rotate about a frictionless axle through its center O, as shown in the cross-sectional view in the figure. A rope wrapped around the outer radius R1 = 1.0 m exerts a force of magnitude F1 = 5.0 N to the right. A second rope wrapped around another section of radius R2 = 0.50 m exerts a force of magnitude F2 = 6.0 N downward. How many radians does the cylinder rotate through in the first 5.0 seconds, if it starts from rest?

A

5.0 rad

81
Q

A compressed gas with a total mass of is stored in a spherical container having a radius of 0.521 m. What is the density of the compressed gas?

A

181 kg/m3

82
Q

A barge with vertical sides is 10 m wide and 60 m long and is floating in fresh water of density 1000 kg/m3. How much deeper into the water does the barge sink when 3.0 x 105 kg of coal are loaded on the barge?

A

50 cm

83
Q

A 12,000-N car is raised using a hydraulic lift, which consists of a U-tube with arms of unequal areas, filled with oil and capped at both ends with tight-fitting pistons. The wider arm of the U-tube has a radius of 18.0 cm and the narrower arm has a radius of 5.00 cm. The car rests on the piston on the wider arm of the U-tube. The pistons are initially at the same level. What is the initial force that must be applied to the smaller piston in order to start lifting the car? For purposes of this problem, neglect the weight of the pistons.

A

926 N

84
Q

A circular window 30 cm in diameter in a submarine can withstand a net maximum force of 5.20 × 105 N without damage. What is the maximum depth in a fresh-water lake to which the submarine can go without damaging the window? The density of fresh water is 1000 kg/m3.

A

750 m

85
Q

A container has a vertical tube, whose inner radius is 24.00 mm, connected to it at its side, as shown in the figure. An unknown liquid reaches level A in the container and level B in the tube–level A being 5.0 cm higher than level B. The liquid supports a 20-cm high column of oil, between levels B and C, whose density is The mass of the oil is closest to

A

210

86
Q

A pressurized cylindrical tank, 5.0 m in diameter, contains water that emerges from the pipe at point C with a speed of as shown in the figure. Point A is 10 m above point B and point C is 3.0 m above point B. The area of the pipe at point B is and the pipe narrows to an area of at point C. Assume that the water is an ideal fluid in laminar flow. The density of water is 1000 kg/m3 The mass flow rate in the pipe is closest to

A

520 Kg/s.

87
Q

A rectangular box of negligible mass measures 5.0 m long, 1.0 m wide, and 0.50 m high. How many kilograms of mass can be loaded onto the box before it sinks in a lake having water of density 1000 kg/m3?

A

2.5 × 103 kg

88
Q

An incompressible ideal fluid flows steadily through a pipe that has a change in diameter. The fluid speed at a location where the pipe diameter is 8.0 cm is 1.28 m/s. What is the fluid speed at a location where the diameter has narrowed to 4.0 cm?

A

5.1 m/s

89
Q

A 4.0-kg cylinder of solid iron is supported by a string while submerged in water. What is the tension in the string? The density of iron is 7860 kg/m3 and that of water is 1000 kg/m3.

A

34 N

90
Q

A 1.00-m3 object floats in water with 20.0% of its volume above the waterline. What does the object weigh out of the water? The density of water is 1000 kg/m3.

A

7,840 N

91
Q

A steel ball sinks in water but floats in a pool of mercury, which is much denser than water. Where is the buoyant force on the ball greater?

A

floating on the mercury

92
Q

A wooden block contains some nails so that its density is exactly equal to that of water. If it is placed in a tank of water and released from rest when it is completely submerged, it will

A

remain where it is released.

93
Q

Water flows through a pipe. The diameter of the pipe at point B is larger than at point A. Where is the water pressure greatest?

A

at point A

94
Q

A 10-kg piece of aluminum sits at the bottom of a lake, right next to a 10-kg piece of lead, which is much denser than aluminum. Which one has the greater buoyant force on it?

A

the aluminum

95
Q

Salt water has greater density than fresh water. A boat floats in both fresh water and in salt water. Where is the buoyant force greater on the boat?

A

The buoyant force is the same in both cases.

96
Q

A hollow sphere of negligible mass and radius R is completely filled with a liquid so that its density is ρ. You now enlarge the sphere so its radius is 2R and completely fill it with the same liquid. What is the density of the enlarged sphere?

A

p

97
Q

As shown in the figure, fluid fills a container having several sections. At which of the indicated points is the pressure greatest?

A

The pressure is the same at each of the labeled points.

98
Q

Substance A has a density of 3 g/cm3 and substance B has a density of 4 g/cm3. In order to obtain equal masses of these two substances, what must be the ratio of the volume of A to the volume of B?

A

VA/VB = 4/3

99
Q

A 50-cm3 block of wood is floating on water, and a 50-cm3 chunk of iron is totally submerged in the water. Which one has the greater buoyant force on it?

A

the iron

100
Q

When you blow some air above a paper strip, the paper rises. This happens because

A

the air above the paper moves faster and the pressure is lower.

101
Q

A brass rod is 69.5 cm long and an aluminum rod is 49.3 cm long when both rods are at an initial temperature of 0° C. The rods are placed in line with a gap of 1.2 cm between them, as shown in the figure. The distance between the far ends of the rods is maintained at 120.0 cm throughout. The temperature of both rods is raised equally until they are barely in contact. At what temperature does contact occur? The coefficients of linear expansion of brass and aluminum are 2.0 ×10-5 K-1 (brass) and 2.4 × 10-5 K-1 (aluminum).

A

470 C

102
Q

A glass beaker of unknown mass contains of water. The system absorbs of heat and the temperature rises as a result. What is the mass of the beaker? The specific heat of glass is 0.18 cal/g ∙ °C, and that of water is 1.0 cal/g ∙ C°.

A

140 g

103
Q

A large vat contains 1.000 L of water at 20°C. What volume will this water occupy when it is heated up to 80°C? Water has a volume expansion coefficient of 210 × 10-6 K-1.

A

1.013 L

104
Q

A machine part consists of 0.10 kg of iron (of specific heat 470 J/kg ∙ K ) and 0.16 kg of copper (of specific heat 390 J/kg ∙ K). How much heat must be added to the gear to raise its temperature from 18°C to 53°C?

A

3800 J

105
Q

A 24.0-L tank contains ideal helium gas at 27°C and a pressure of 22.0 atm. How many moles of gas are in the tank? (R = 8.31 J/mol ∙ K, 1 atm = 101 kPa)

A

76.0 mol

106
Q

A blacksmith is flattening a steel plate having dimensions 10 cm × 15 cm × 1 mm. He has heated the plate to 900 K. If the emissivity of the plate is 0.75, at what rate does it lose energy by radiation? Ignore any heat exchange with the surroundings. (σ = 5.67 × 10-8 W/m2 ∙ K4)

A

850 W

107
Q

A 5.00-g lead BB moving at 44.0 m/s penetrates a wood block and comes to rest inside the block. If half of its kinetic energy is absorbed by the BB, what is the change in the temperature of the BB? The specific heat of lead is 128 J/kg ∙ K.

A

3.78 K

108
Q

A 20.0-L pressure vessel holds 2.00 mol of oxygen at 30°C. What is the pressure inside the vessel? (R = 8.31 J/mol ∙ K)

A

252 kPa

109
Q

A runner generates 1260 W of thermal energy. If this heat has to be removed only by evaporation, how much water does this runner lose in 15 minutes of running? The latent heat of vaporization of water is 22.6 × 105 J/kg.

A

500 g

110
Q

A 4.2-L flask of ideal neon gas (which is monatomic) is at a pressure of 3.3 atm and a temperature of 450 K. The atomic mass of neon is 20.2 g/mol. How many neon atoms are in the flask? (R = 8.31 J/mol ∙ K, 1 atm = 101 kPa, NA = 6.022 × 1023 molecules/mol)

A

2.3 × 1022

111
Q

On a cold day, a piece of metal feels much colder to the touch than a piece of wood. This is due to the difference in which one of the following physical properties of these materials?

A

thermal conductivity

112
Q

The coefficient of linear expansion for aluminum is 1.8 × 10-6 K-1. What is its coefficient of volume expansion?

A

5.4 × 10-6 K-1

113
Q

In a given reversible process, the temperature of an ideal gas is kept constant as the gas is compressed to a smaller volume. Which one of the following statements about the gas is correct?

A

The gas must release heat to its surroundings.

114
Q

Two metal spheres are made of the same material and have the same diameter, but one is solid and the other is hollow. If their temperature is increased by the same amount,

A

the two spheres remain of equal size.

115
Q

An object having a fixed emissivity of 0.725 radiates heat at a rate of 10 W when it is at an absolute temperature T. If its temperature is doubled to 2T, at what rate will it now radiate?

A

160 W

116
Q

A thermally isolated system is made up of a hot piece of aluminum and a cold piece of copper, with the aluminum and the copper in thermal contact. The specific heat capacity of aluminum is more than double that of copper. Which object experiences the greater temperature change during the time the system takes to reach thermal equilibrium?

A

It is impossible to tell without knowing the masses.

117
Q

By what primary heat transfer mechanism does the sun warm the earth?

A

radiation

118
Q

Object 1 has three times the specific heat capacity and four times the mass of Object 2. The two objects are heated from the same initial temperature, T0, to the same final temperature Tf. During this process, if Object 1 absorbs heat Q, the amount of heat absorbed by Object 2 will be

A

12Q

119
Q

A thermally isolated system is made up of a hot piece of aluminum and a cold piece of copper, with the aluminum and the copper in thermal contact. The specific heat capacity of aluminum is more than double that of copper. Which object experiences the greater magnitude gain or loss of heat during the time the system takes to reach thermal equilibrium?

A

Neither one; both of them experience the same size gain or loss of heat.

120
Q

Which two temperature changes are equivalent?

A

1 C° = 1 K

121
Q

Which one of the following is a true statement?

A

All of these statements are false.

122
Q

The second law of thermodynamics leads us to conclude that

A

disorder in the universe is increasing with the passage of time.

123
Q

When water at 0°C freezes, the entropy of the water

A

decreases

124
Q

A Carnot cycle consists of

A

two adiabats and two isotherms.

125
Q

Which of the following is a false statement?

A

The entropy of an isolated system must be conserved (it remains constant).

126
Q

A certain gas is compressed adiabatically. The amount of work done on the gas is 800 J. What is the change in the internal (thermal) energy of the gas?

A

800 J

127
Q

A heat engine receives 7000 J of heat and loses 3000 J in each cycle. What is the efficiency of this engine?

A

57%

128
Q

A sealed rigid tank contains 29 moles of an ideal gas, at an initial temperature of The pressure of the gas is increased until the final pressure equals 1.90 times the initial pressure. The heat capacity at constant pressure of the gas is How much heat is absorbed by the gas during this process? (R = 8.31 J/mol ∙ K)

A

110 kJ

129
Q

A heat engine having the maximum possible efficiency has an efficiency of 35.0% when operating between two heat reservoirs. If the temperature of the hot reservoir is 700 K, what is the temperature of the cold reservoir?

A

455 K

130
Q

A fluid in an insulated, flexible bottle is heated by a high resistance wire and expands. If of heat is applied to the system and it does of work, how much does the internal (thermal) energy of the fluid change?

A

4.0 kJ

131
Q

A Carnot air conditioner has a coefficient of performance of 17.0 and removes 72.0 MJ of heat from the interior of a house every hour. How much power does it consume?

A

1180 W

132
Q

The figure shows a pV diagram for a cycle of a heat engine for which QH = 59 J. What is the thermal efficiency of the engine?

A

17%

Physics Questions (2 decks)

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