FINAL EXAM Multiple Choice
If A - B = 0, then the vectors A and B have equal magnitudes and are directed in the opposite directions from each other.
False
If all the components of a vector are equal to 1, then that vector is a unit vector.
False
If the acceleration of an object is negative, the object must be slowing down.
False
If two forces of equal magnitude act on an object that is hinged at a pivot, the force acting farther from the pivot must produce the greater torque about the pivot.
False
In order to get an object moving, you must push harder on it than it pushes back on you. A) True B) False
False
In order to lift a bucket of concrete, you must pull up harder on the bucket than it pulls down on you. A) True B) False
False
There must be equal amounts of mass on both side of the center of mass of an object.
False
Water flows through a pipe having a varying width. More water flows per second through the wide section than through the narrow section because there is more room for it to flow.
False
A monkey is sitting at the top of a tree 20 m above ground level. A person standing on the ground wants to feed the monkey. He uses a bow and arrow to launch the food to the monkey. If the person knows that the monkey is going to drop from the tree at the same instant that the person launches the food, how should the person aim the arrow containing the food? Air resistance is small enough to be ignored.
He should aim it at the monkey.
Suppose that an object is moving with constant nonzero acceleration. Which of the following is an accurate statement concerning its motion?
In equal times its velocity changes by equal amounts
What does the slope of the line on a position-time plot describe about an object's motion?
It describes how fast and in what direction the object is moving.
What does the slope of the tangent line at a point in time on a velocity-time plot describe about an object's motion?
It describes the acceleration value.
A ball rolls off the table and free falls to the ground. Which statement accurately describes its acceleration?
Its acceleration is downward but remains a constant value as it falls.
Suppose that a car traveling to the west (the -x direction) begins to slow down as it approaches a traffic light. Which statement concerning its acceleration in the x direction is correct?
Its acceleration is positive but its velocity is negative.
An object is moving horizontally at a constant speed. Which one of the following statements is true of the object?
Its kinetic energy is constant.
An object is moving uphill at a constant speed. Which one of the following statements is true of the object?
Its kinetic energy is constant.
An object is moving horizontally and slowing down. Which one of the following statements is true of the object?
Its kinetic energy is decreasing.
Which is the best definition of the term kinetic energy?
Kinetic energy is the energy due to motion.
Two objects have masses m and 5m, respectively. They both are placed side by side on a frictionless inclined plane and allowed to slide down from rest. A) It takes the lighter object 10 times longer to reach the bottom of the incline than the heavier object. B) The two objects reach the bottom of the incline at the same time. C) It takes the lighter object 5 times longer to reach the bottom of the incline than the heavier object. D) It takes the heavier object 10 times longer to reach the bottom of the incline than the lighter object. E) It takes the heavier object 5 times longer to reach the bottom of the incline than the lighter object.
The two objects reach the bottom of the incline at the same time.
If A > B, under what condition is the absolute value of (A - B) = A - B?
Vectors A and B are in the same direction.
If an irregularly shaped object (such as a wrench) is dropped from rest in a classroom and feels no air resistance, it will
accelerate but will not spin.
When a rigid body rotates about a fixed axis, all the points in the body have the same
angular acceleration
A pilot drops a package from a plane flying horizontally at a constant speed. Neglecting air resistance, when the package hits the ground the horizontal location of the plane will
be over the package.
In a perfectly ELASTIC collision between two perfectly rigid objects
both the momentum and the kinetic energy of the system are conserved.
You are driving a late model convertible car at the 65 mph speed limit with its soft flexible roof closed up and the windows closed. You observe that the roof
bows outward
The motion of a particle is described in the velocity versus time graph shown in the figure. We can say that its speed.
decreases and then increases.
A ball is thrown directly upward and experiences no air resistance. Which one of the following statements about its motion is correct?
The acceleration is downward during the entire time the ball is in the air.
When an object is solely under the influence of conservative forces, the sum of its kinetic and potential energies does not change.
True
A 20-ton truck collides with a 1500-lb car and causes a lot of damage to the car. During the collision A) the force of on the truck due to the collision is exactly equal to the force on the car. B) the force on the truck due to the collision is slightly greater than the force on the car. C) the force on the car due to the collision is much greater than the force on the truck. D) the car and the truck have the same magnitude acceleration
the force of on the truck due to the collision is exactly equal to the force on the car.
While an object is in projectile motion (with upward being positive) with no air resistance
the horizontal component of its velocity remains constant and the vertical component of its acceleration is equal to -g.
Under what condition is the absolute value of (A - B) = A + B?
Vectors A and B are in opposite directions.
Alice and Tom dive from an overhang into the lake below. Tom simply drops straight down from the edge, but Alice takes a running start and jumps with an initial horizontal velocity of 25 m/s. Neither person experiences any significant air resistance. Compare the time it takes each of them to reach the lake below.
Alice and Tom will reach the surface of the lake at the same time.
Two stones, one of mass m and the other of mass 2m, are thrown directly upward with the same velocity at the same time from ground level and feel no air resistance. Which statement about these stones is true?
At its highest point, the heavier stone will have twice as much gravitational potential energy as the lighter one because it is twice as heavy.
Two identical balls are thrown directly upward, ball A at speed v and ball B at speed 2v, and they feel no air resistance. Which statement about these balls is correct?
Ball B will go four times as high as ball A because it had four times the initial kinetic energy.
A ball is projected horizontally from the top of a cliff. At the same moment, a second identical ball is dropped from rest from the same location. Which ball lands on the ground first? Assume free fall motion.
Both balls land on the ground at the same time.
Is it possible for a system to have negative potential energy?
Yes, since the choice of the zero of potential energy is arbitrary.
In a collision between two objects having unequal masses, how does magnitude of the impulse imparted to the lighter object by the heavier one compare with the magnitude of the impulse imparted to the heavier object by the lighter one?
Both objects receive the same impulse.
You are standing on a skateboard, initially at rest. A friend throws a very heavy ball towards you. You can either catch the object or deflect the object back towards your friend (such that it moves away from you with the same speed as it was originally thrown). What should you do in order to MINIMIZE your speed on the skateboard?
Catch the ball.
An object is moving forward with a constant velocity. Which statement about this object MUST be true? A) The net force on the object is in the forward direction. B) The acceleration of the object is in the forward direction. C) No forces are acting on the object. D) The net force on the object is zero.
D) The net force on the object is zero
A crate is sliding down an inclined ramp at a constant speed of 0.55 m/s. The vector sum of all the forces acting on this crate must point down the ramp. A) True B) False
False
As a tile falls from the roof of a building to the ground its momentum is conserved.
False
A ball rolls off the table and free falls to the ground. Which statement accurately describes its motion as it falls to the ground?
Its horizontal speed does not change but its vertical speed increases.
A woman is straining to lift a large crate, without success because it is too heavy. We denote the forces on the crate as follows: P is the upward force the woman exerts on the crate, C is the vertical contact force exerted on the crate by the floor, and W is the weight of the crate. How are the magnitudes of these forces related while the woman is trying unsuccessfully to lift the crate? A) P = C B) P + C < W C) P + C > W D) P + C = W
P + C = W
A box of mass m is pulled with a constant acceleration a along a horizontal frictionless floor by a wire that makes an angle of 15° above the horizontal. If T is the tension in this wire, then A) T < ma B) T > ma C) T = ma
T > ma.
How can a velocity-time graph be used to determine the acceleration of an object at a given instant in time?
The acceleration is the slope of the tangent line at that particular point in time on the graph.
A ball is projected horizontally from the top of a cliff and free falls to the ground. Which one of the following statements accurately describes the ball's motion?
The ball moves horizontally with a constant velocity but accelerates downward.
Which of the following is an accurate statement?
The magnitude of a vector is independent of the coordinate system used.
A ball is dropped from the ceiling and free falls to the floor. Which one of the following statements regarding the ball's motion is correct?
The position change of the ball during any second is greater than it was during the previous second.
The angular momentum of a system remains constant
when no torque acts on the system.
Consider two less-than-desirable options. In the first you are driving 30 mph and crash head-on into an identical car also going 30 mph. In the second option you are driving 30 mph and crash head-on into a stationary brick wall. In neither case does your car bounce off the thing it hits, and the collision time is the same in both cases. Which of these two situations would result in the greatest impact force?
The force would be the same in both cases.
If the eastward component of vector A is equal to the westward component of vector B and their northward components are equal. Which one of the following statements about these two vectors is correct?
The magnitude of vector A is equal to the magnitude of vector B.
Consider the plot shown at the right. Which description below is consistent with the graph? (velocity v time graph red line)
The object accelerates at a low rate; it then moves with a higher rate of acceleration.
Consider the plot shown at the right. Which description below is consistent with the graph? (position v time graph)
The object is at rest and then moves in the negative direction at a constant speed.
Consider the plot shown at the right. Which description below is consistent with the graph?
The object moves in the positive direction at a constant speed; it then slows to a stop.
A small car has a head-on collision with a large truck. Which of the following statements concerning the magnitude of the average force due to the collision is correct?
The small car and the truck experience the same average force.
A girl throws a stone from a bridge. Consider the following ways she might throw the stone. The speed of the stone as it leaves her hand is the same in each case, and air resistance is negligible. Case A: Thrown straight up. Case B: Thrown straight down. Case C: Thrown out at an angle of 45° above horizontal. Case D: Thrown straight out horizontally.
The speed will be the same in all cases.
Two balls roll off the table at the same time and free fall to the ground. Ball A is moving at 1 m/s when it rolls off the table. Ball B is moving at 2 m/s when it rolls off the table. Which ball has the greatest acceleration as it falls to the ground?
The two balls have the same acceleration.
Two balls roll off the table at the same time and free fall to the ground. Ball A is moving at 1 m/s when it rolls off the table. Ball B is moving at 2 m/s when it rolls off the table. Which ball hits the ground first?
The two balls land at the same time.
Which statement describes how the velocity of an object changes as it free falls?
The velocity changes by the same amount each consecutive second.
How can the velocity of an object be determined from a position-time graph of its motion?
The velocity is the slope of the line on the graph.
A ball is thrown upward towards a ceiling. Which one of the following statements regarding the ball's motion is correct? Neglect air resistance.
The velocity vector points in the opposite direction as the acceleration vector.
A ball is projected horizontally from the top of a cliff. At the same moment, a second identical ball is dropped from rest from the same location. Which one of the following quantities is NOT the same for the two balls? Assume free fall motion.
The velocity with which the two balls hit the ground.
Two objects are thrown from the top of a tall building and experience no appreciable air resistance. One is thrown up, and the other is thrown down, both with the same initial speed. What are their speeds when they hit the street?
They are traveling at the same speed.
Jan and Len throw identical rocks off a tall building at the same time. The ground near the building is flat. Jan throws her rock straight downward. Len throws his rock downward and outward such that the angle between the initial velocity of the rock and the horizon is 30°. Len throws the rock with a speed twice that of Jan's rock. If air resistance is negligible, which rock hits the ground first?
They hit at the same time.
If the graph of the velocity as a function of time for an object is a horizontal line, that object cannot be accelerating.
True
The magnitude of a vector can never be less than the magnitude of one of its components.
True
A dog is standing in the bed of a pickup truck. The bed is coated with ice, causing the force of friction between the dog and the truck to be zero. The truck is initially at rest, and then accelerates to the right, moving along a flat road. As seen from a stationary observer (watching the truck move to the right), the dog A) does not move left or right, but the back of the truck moves towards the dog. B) moves to the left, as the truck moves to the right, causing the dog to slide towards the back of the truck. C) moves to the right, but not as quickly as the truck is moving to the right, causing it to slide towards the back of the truck. D) moves to the right at the same rate as the truck, so it doesn't slide
does not move left or right, but the back of the truck moves towards the dog.
You swing a bat and hit a heavy box with a force of 1500 N. The force the box exerts on the bat is A) exactly 1500 N whether or not the box moves. B) exactly 1500 N only if the box does not move. C) greater than 1500 N if the box moves. D) less than 1500 N if the box moves. E) greater than 1500 N if the bat bounces back.
exactly 1500 N whether or not the box moves
The figure shows the velocity of a particle as it travels along the x-axis. What is the direction of the acceleration at t = 0.5 s?
in the -x direction
As the speed of a moving fluid increases, the pressure in the fluid
increases
A baseball is thrown vertically upward and feels no air resistance. As it is rising
its momentum is not conserved, but its mechanical energy is conserved.
For general projectile motion, when the projectile is at the highest point of its trajectory
its velocity is perpendicular to the acceleration.
Salt water is more dense than fresh water. A ship floats in both fresh water and salt water. Compared to the fresh water, the volume of salt water displaced by the ship is
less than the volume of fresh water.
A brick is resting on a rough incline as shown in the figure. The friction force acting on the brick, along the incline, is A) greater than the weight of the brick. B) zero. C) less than the weight of the brick. D) equal to the weight of the brick.
less than the weight of the brick.
What factors does the kinetic energy of an object depend upon?
mass and speed
A small glider is coasting horizontally when suddenly a very heavy piece of cargo falls out of the bottom of the plane. You can neglect air resistance. Just after the cargo has fallen out
neither the cargo nor the plane change speed.
Suppose you are playing hockey on a new-age ice surface for which there is no friction between the ice and the hockey puck. You wind up and hit the puck as hard as you can. After the puck loses contact with your stick, the puck will A) not slow down or speed up. B) speed up a little, and then slow down. C) start to slow down. D) speed up a little, and then move at a constant speed.
not slow down or speed up.
When can we be certain that the average velocity of an object is always equal to its instantaneous velocity?
only when the velocity is constant
A rock is under water in a shallow lake. As the rock sinks deeper and deeper into water, the buoyant force on it
remains constant.
Suppose the force of the air drag on an object is proportional to the speed of the object and in the direction opposite the object's velocity. If you throw an object upward, the magnitude of its acceleration is greatest A) at the top of its trajectory. B) right after the object is released. C) The acceleration of the object is the same throughout the entire trajectory.
right after the object is released.
A solid sphere and hollow sphere all have equal masses and radii and are of uniform density. If the two are released simultaneously at the top of an inclined plane and roll without slipping, which one will reach the bottom first? The hollow sphere has a greater moment of inertia that a solid sphere with the same mass and radius.
solid sphere
The figure represents the velocity of a particle as it travels along the x-axis. At what value (or values) of t is the instantaneous acceleration equal to zero?
t = 1 s
At a certain depth in the ocean, the absolute pressure is p. If you go to twice that depth (treating the water as incompressible)
the absolute pressure will be less than 2p.
When you blow some air above the upper face of a paper strip, the paper rises. This occurs because
the air above the upper face of the paper moves faster, which makes the pressure lower than at the lower face.
A cup of water containing an ice cube at 0°C is filled to the brim. The tip of the ice cube sticks out of the surface. As the ice melts, you observe that
the cup overflows.
When a parachutist jumps from an airplane, he eventually reaches a constant speed, called the terminal speed. Once he has reached terminal speed A) his speed is equal to g. B) the force of air drag on him is equal to g C) the force of air drag on him is equal to his weight D) the force of air drag on him is equal to zero E) his acceleration is equal to g
the force of air drag on him is equal to his weight
In an INELASTIC collision between two objects
the momentum of the system is conserved but the kinetic energy of the system is not conserved.
If the torque on an object adds up to zero
the object could be both turning and accelerating linearly.
Momentum is _____.
the product of the mass and velocity of an object
Alice and Tom dive from an overhang into the lake below. Tom simply drops straight down from the edge, but Alice takes a running start and jumps with an initial horizontal velocity of 25 m/s. Neither person experiences any significant air resistance. Just as they reach the lake below
the speed of Alice is larger than that of Tom.
A ball is tossed vertically upward. When it reaches its highest point (before falling back downward) A) the velocity, acceleration, and the force of gravity on the ball all reverse direction. B) the velocity is zero, the acceleration is zero, and the force of gravity acting on the ball is zero. C) the velocity is zero, the acceleration is directed downward, and the force of gravity acting on the ball is directed downward. D) the velocity and acceleration reverse direction, but the force of gravity on the ball remains downward. E) the velocity is zero, the acceleration is zero, and the force of gravity acting on the ball is directed downward.
the velocity is zero, the acceleration is directed downward, and the force of gravity acting on the ball is directed downward.
A box slides down a frictionless plane inclined at an angle θ above the horizontal. The gravitational force on the box is directed A) at an angle θ below the inclined plane. B) parallel to the plane in the same direction as the movement of the box. C) vertically D) parallel to the plane in the opposite direction as the movement of the box E) perpendicular to the plane
vertically