Physics Multiple Choice - Midterm Flashcards
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For general projectile motion, the horizontal component of a projectile’s acceleration
Remains a non-zero constant
The average velocity of a car traveling with a constant acceleration during a certain time interval is equal to the mean of the velocities at the beginning and end of that time interval. (T/F)
T
Suppose that an object is moving with constant acceleration. Which of the following is an accurate statement concerning its motion?
In equal times its velocity changes by equal amounts
A rock is thrown upwards at an angle of 40° with respect to the horizontal. As the rock is rising in its trajectory, the horizontal component of its velocity
remains the same
A boy kicks a football with an initial velocity of 20m/s at an angle of 25° above the horizontal. The magnitude of the acceleration of the ball while it is in flight is
9.8m/s^2
When a parachutist jumps from an airplane, he eventually reaches a constant speed, called the terminal velocity. This is an example of
All of Newton’s laws apply to this situation
Force is a vector quantity. (T/F)
T
Mass is a measure of how difficult it is to change the velocity of an object. (T/F)
T
A force is required for an object to move. (T/F)
F
An object always moves in the direction of the net force pushing on it (T/F)
F
It is possible to have zero acceleration, and still be moving. (T/F)
T
An object is in free fall as soon as it is released, whether it is dropped from rest, thrown downward, or thrown upward. (T/F)
T
An object thrown downward does not experience free fall. (T/F)
F
When the velocity and acceleration of an object have the same sign, the speed of the object increases. (T/F)
T
Free fall is the motion of an object subject only to the influence of gravity. (T/F)
T
When is the average velocity of an object equal to the instantaneous velocity?
only when the velocity is constant
Two objects are thrown vertically upwards simultaneously, one on the surface of Earth and the other on the surface of the Moon. Both have an initial velocity of 20m/s. Both objects will take the same time to reach the highest point of their trajectory. (T/F)
F
The vertical component of the acceleration of a projectile remains constant during the entire trajectory of the projectile. (T/F)
T
If the acceleration vector of an object is directed parallel to the velocity vector,
the object is speeding up
A girl kicks a soccer ball with an initial velocity of 25m/s at an angle of 30° above the horizontal. The horizontal component of the velocity of the ball is described by one of the following statements.
it remains constant during the ball’s flight
The acceleration of an object does not have to be in the same direction as the net force applied to it (T/F)
F
When a ball is thrown upwards, it reaches its maximum height when the force pushing it up is equal to its weight (T/F)
F
The force you exert of Earth is insignificant compared to the force Earth exerts on you (T/F)
T
The mass of an object is fixed, but its weight varies from location to location (T/F)
T
You apply the same force to two objects. Object 1 has mass M and object 2 has mass 5M. The acceleration of object 2 is
one-fifth as that of object 1
A 20-ton truck collides with a 1500lb car and causes a lot of damage to the car. Since a lot of damage is done on the car
the force on the truck is equal to the force on the car
Action - reaction forces are
equal in magnitude but point in opposite directions
A ball is thrown up into the air. At the highest point in its trajectory, the net force on it is
equal to its weight
The force of static friction between two surfaces is parallel to the surface of contact, and in the direction that opposes relative motion (T/F)
T
A constant net force acts on an object. Describe the motion of the object
constant non-zero acceleration
An object is moving with constant velocity. Which of the following statements is true?
The net force on the object is zero
Its more difficult to start moving a heavy carton from rest than it is to keep pushing it with constant velocity, because
μk < μs
When a car goes around a curve, it has a tendency to skid outwards. Is the frictional force between the tires and the ground that keeps the car from skidding kinetic or static?
static
Work done by a force on an object can be a positive or a negative quantity (T/F)
T
Work done by the force of friction can be positive or negative (T/F)
F
Kinetic energy is a scalar quantity (T/F)
T
Kinetic energy is proportional to mass (T/F)
T
Power is a vector quantity (T/F)
F
Can work be done on a system if there is no motion?
no, since work involves a non-zero displacement
A person applies a constant force of 20N to a rock of mass 1000kg, for a total of 20 seconds. What is the work done by this person if the rock does not move at all by this applied force?
0 J
The SI unit of work is expressed as
Joule
The gravitational force is a conservative force (T/F)
T
The sum of the kinetic and potential energies of an object is conserved only when the object is under the influence of conservative forces (T/F)
T
The frictional force is a conservation force (T/F)
F
You need to load a crate of mass m onto the bed of a truck. One possibility is to lift the crate straight up over a height h, equal to height of the truck’s bed. The work done in this case is W1. The other possibility is to slide the crate up the frictionless ramp of length L. In this case you person work W2. Which statement is true?
W1 = W2
The quantity mgy is
the gravitational potential energy of the object
You and your friend want to go to the top of the Eiffel Tower. Your friend takes the elevator straight up. You decide to walk up the spiral stairway, taking longer to do so. Compare the gravitational potential energy (U) of you and your friend, after you both reach the top.
Both of you have the same amount of potential energy
Impulse is a scalar quantity (T/F)
F
Describe the energy of a car driving up a hill
both kinetic and potential
Linear momentum is a vector quantity (T/F)
T
An acorn falls from a tree. Compare its kinetic energy K, to its potential energy U
K increases and U decreases
When objects stick together after colliding, the colliding is completely elastic (T/F)
F
A freight car moves along a frictionless lever railroad track at constant speed. The freight car is open on top. A large load of coal is suddenly dumped into the car. What happens to the speed of the freight car?
it decreases
A rubber ball and a lump of putty have equal mass. They are thrown with equal speed against a wall. The ball bounces back with nearly the same speed with which it hit. The putty sticks to the wall. Which objects experiences the greater momentum change?
the ball
An inelastic collision of two objects is characterized by the following
Total momentum of the system is conserved
A rock is thrown at some angle above the horizontal with a certain velocity. It reaches its highest points and starts falling down. What is the velocity of the rock at the highest point of its trajectory?
It is equal to its initial horizontal velocity
A rock is thrown at some angle above the horizontal with a certain velocity. It reaches its highest point and starts falling down. What is the magnitude of the acceleration of the rock at the highest point of its trajectory
9.8m/s^2
A rock is thrown upwards at an angle of 40° with respect to the horizontal. As the rock is rising in its trajectory, the vertical component of its velocity
decreases
A block of mass M slides down a frictionless plane inclined at an angle θ with the horizontal. The normal reaction force exerted by the plane on the block is
Mg cos θ
You ride on an elevator that is moving with constant downward acceleration while standing on a bathroom scale. The reading on the scale is
less than your true weight, mg
A golf club hits a golf ball with a force of 2400N. The golf ball hits the club with a force
exactly 2400 N
When an object moves at constant speed on a circular path, which of the following is true?
a net force pointing towards the center of the circle acts on the object
The block of mass m is at rest on an inclined plane that makes an angle θ with the horizontal. The force of static friction f must be such that
f = mg sinθ
A block of mass M slides down a frictionless plane inclined at an angle θ with the horizontal. The gravitational force is directed
toward the center of the Earth
Two identical masses are attached by a light string that passes over a small pulley. The table and the pulley are frictionless. The masses are moving
with an acceleration less than g
What force is needed to make an object move in a circle?
centripetal force
If a car slows down with the wheels rolling, is the frictional force between the tires and the ground kinetic or static
static
What type of acceleration does an object moving with constant speed in a circular path experience?
centripetal acceleration
When an object experiences uniform circular motion, the direction of the net force is
is directed toward the center of the circular path
A roller coaster car is on a track that forms a circular loop in the vertical plane. If the car is to just maintain contact with track at the top of the loop, what is the minimum value for its centripetal acceleration at this point?
g downward
An elastic collision of two objects is characterized by the following
Both are true
Potential energy represented by the equation PE = mgh is a vector quantity (T/F)
F
Non-conservative forces can change the mechanical energy of a system (T/F)
T
If work is done on a system by non-conservative forces, the total mechanical energy of a system stays constant (T/F)
F
You throw a ball straight up. Compare the sign of the work done by gravity while the ball goes up with the sign of the work done by gravity while it goes down.
Work is - on the way up and + on the way down
3 MULTIPLE CHOICE OPTIONS
James and John dive from an overhang into the lake below. James simply drops straight down from the edge. John takes a running start and jumps with an initial horizontal velocity of 25 m/s. Compare the time it takes to reach the lake below.
James and John will reach the surface of the lake at the same time
Kinetic energy may be positive or negative (T/F)
F
Potential energy may be positive or negative (T/F)
T
The quantity 1/2kx^2 is
the elastic potential energy of the object
An object is released from rest a height h above the ground. A second object with four times the mass of the first if released from the same height. The potential energy of the second object compared to the first is
four times as much
A block of mass m slides without friction on a table with speed v. It hits and compresses a spring of force constant k by a distance l. The spring then expands again ejecting the block in the opposite direction as it was originally traveling. Neglecting the mass of the spring, what is the speed of the object it is ejected by the spring?
v
A 0.200 kg mass attached to the end of a spring causes it to stretch 5.0 cm. If another 0.200 kg mass is added to the spring, the potential energy of the spring will be
4 times as much
A roller coaster car (mass = M) is on a track that forms a circular loop (radius = r) in the vertical plane. If the car is to just maintain contact with the track at the top of the loop, what is the minimum value for its speed at that point?
(rg)^1/2
The total mechanical energy of a system
is constant, only if conservative forces act
Neglecting air resistance, when you toss a stone straight up in the air from Earth’s surface, which of the following statements is true for the upward motion of the stone.
the stone’s kinetic energy decreases while its gravitational potential energy increases
A lightweight object and a very heavy object are sliding with equal speeds along a level frictionless surface. They both slide up the same frictionless hill. Which rises to a greater height?
They both slide to the same height
