midterm Flashcards
When a ball is thrown straight up with no air resistance, the acceleration at its highest point
…is downward
Suppose that a car traveling to the west (-x direction) begins to slow down as it approaches a traffic light. Which statement concerning its acceleration must be correct?
its acceleration is positive
Two displacement vectors have magnitudes of 5.0 m and 7.0 m, respectively. If these two vectors are added together, the magnitude of the sum
could be as small as 2.0 m or as large as 12 m
The eastward component of vector is equal to the westward component of vector and their northward components are equal. Which one of the following statements must be correct for these two vectors?
The magnitude of vector must be equal to the magnitude of vector .
A horse pulls a cart with force . As a result of this force the cart accelerates with constant acceleration. The magnitude of the force that the cart exerts on the horse
equal to the magnitude of .
Two objects have masses m and 5m, respectively. They both are placed side by side on a frictionless inclined ramp and allowed to slide down from rest without any air resistance. Which one of the following statements about these objects is correct?
The two objects reach the bottom of the ramp at exactly the same time.
A push of magnitude P acts on a box of weight W as shown in the figure. The push is directed at an angle θ below the horizontal, and the box remains a rest. The box rests on a horizontal surface that has some friction with the box. The normal force on the box due to the floor is equal to
Correct W + P sin θ.
A train travels at a constant speed of 60.4 mi/h for 101.5 min. What distance does the train cover expressed to the correct number of significant figures?
102 mi
A ball is projected upward at time t = 0 s, from a point on a flat roof 10 m above the ground. The ball rises and then falls with insignificant air resistance, missing the roof, and strikes the ground. The initial velocity of the ball is Consider all quantities as positive in the upward direction. At time the vertical velocity of the ball is closest to
0 m/s.
To determine the height of a bridge above the water, a person drops a stone and measures the time it takes for it to hit the water. If the time is 2.3 s, what is the height of the bridge? Neglect air resistance.
26 m
A swimmer heading directly across a river that is 200 m wide reaches the opposite bank in 6 min 40 s. During this swim, she is swept downstream 480 m. What is the speed of the current?
1.2 m/s
A player throws a football 50.0 m at 61.0° north of west. What is the westward component of the displacement of the football?
24.2 m
The figure shows an acceleration-versus-force graph for three objects pulled by wires. If the mass of object 2 is 36 kg, what are the masses of objects 1 and 3?
12 kg and 90 kg
A 50-kg box is resting on a horizontal floor. A force of 250 N directed at an angle of 30.0° below the horizontal is applied to the box. The coefficient of static friction between the box and the surface is 0.40, and the coefficient of kinetic friction is 0.30. What is the force of friction on the box?
220 N
A 6.00-kg ornament is held at rest by two light wires that form 30° angles with the vertical, as shown in the figure. An external force of magnitude F acts vertically downward on the ornament. The tension exerted by each of the two wires is denoted by T. A free-body diagram, showing the four forces that act on the box, is shown in the figure. If the magnitude of force F is 410 N, what is the magnitude of the tension T?
271 N
A bead is moving with a speed of 20 m/s at position A on the track shown in the figure. This track is friction-free, and there is no appreciable air resistance. What is the speed of the bead at point C?
34 m/s
A certain battery charger uses 12 W of power. At 6.0 cents per kilowatt-hour, how much does it cost to charge batteries for a full day?
1.7 c
In the product A ∙ B ∙ C, A has 5 significant figures, B has 2 significant figures, and C has 3 significant figures. How many significant figures does the product have?
2
If the answer to your calculation has units of kg ∙ m2/s, what type of quantity could it be? (There could be more than one correct choice).
angular momentum
Two objects of different mass have equal, non-zero kinetic energies. Which object has the greater magnitude momentum?
the heavier object
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?
4
A rocket explodes into two fragments, one 25 times heavier than the other. The magnitude of the momentum change of the lighter fragment is
The same as the momentum change of the heavier fragment.
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?
Deflect the ball back.
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
completely inelastic.
