AP Physics Dynamics test

Which of the following is a valid force that could be exerted on a baseball?

The force on a baseball being hit by a bat

In the figure, a hand is pushing on block B to the right, causing both blocks to move to the right across a rough surface at a constant speed. Compare the force that pushes block B to the right to the force that pushes block A to the right.

The force that pushes block A to the right is smaller than the force that pushes block B to the right.

Students connect a spring scale to a block on a rough horizontal surface. The students use the spring scale to measure the magnitude of the horizontal force needed to pull the block at a constant speed. Which of the following statements explains why two forces exerted between objects are equal in magnitude?

The frictional forces that the block and the surface exert on each other, because objects always exert forces of equal magnitude on each other.

A satellite orbits Earth. The only force on the satellite is the gravitational force exerted by Earth. How does the satellite's acceleration compare to the gravitational field at the location of the satellite? Select two answers.

- The magnitudes of the acceleration and the gravitational field strength are equal. - The gravitational field and the acceleration point in the same direction.

A satellite orbits Earth. The only force on the satellite is the gravitational force exerted by Earth. How does the satellite's acceleration compare to the gravitational field at the location of the satellite? Select two answers.

- The magnitudes of the acceleration and the gravitational field strength are equal. - The gravitational field and the acceleration point in the same direction.

A student must design an experiment to determine the acceleration of a cart that rolls down a small incline after it is released from rest. The student has access to a timer, a meterstick, and a slow-motion camera that takes a photograph every LaTeX: \frac{1}{60}160 of a second. The angle that the incline makes with the horizontal is unknown, and the length of the incline is unknown. Which of the following procedures could the student use to determine the cart's acceleration? Select two answers. Correct!

-Use the slow-motion camera to film the cart as it rolls down the incline alongside a meterstick that is attached to the incline. -Use the timer to record the time it takes the cart to travel alongside a meterstick that is attached to the incline. B

If the mass of block B is 2 kg, the gravitational force exerted on block B is most nearly which of the following?

20 N

A ball traveling at a speed LaTeX: v_0𝑣0 rolls off a desk and lands at a horizontal distance LaTeX: x_0𝑥0 away from the desk, as shown in the figure. The ball is then rolled off of the same desk at a speed of 3 LaTeX: v_0𝑣0. At what horizontal distance will the ball land from the table?

3x0

A 5kg object is released from rest near the surface of a planet such that its gravitational field is considered to be constant. The mass of the planet is unknown. After 2s, the object has fallen 30m. Air resistance is considered to be negligible. What is the gravitational force exerted on the 5 kg object near the planet's surface?

75 N

You are lying on your back on the slope of a grassy hill, watching the clouds go by overhead. Which is the best statement about the force of friction exerted on you by the ground in this situation?

A force of static friction pointing "up the hill", parallel to the surface of the hill, is applied to you by the ground.

A person is standing still while leaning against the wall in a classroom. Which is the best answer regarding the number of forces exerted on her?

At least four

Which of the following is a correct ranking of the normal forces LaTeX: F_{n1},\:F_{n2},\:and\:F_{n3}𝐹𝑛1,𝐹𝑛2,𝑎𝑛𝑑𝐹𝑛3, exerted on the boxes?

F_{n3}>F_{n2}>F_{n1}

How does the magnitude of the force exerted by the stick on the puck LaTeX: F_{puck,\:stick}𝐹𝑝𝑢𝑐𝑘,𝑠𝑡𝑖𝑐𝑘 compare to the magnitude of the force exerted by the puck on the stick LaTeX: F_{stick,\:puck}𝐹𝑠𝑡𝑖𝑐𝑘,𝑝𝑢𝑐𝑘 at the time interval in which the stick is in contact with the puck?

F_{puck,\:stick}=F_{stick,\:puck}

Josh punches his open left hand with his right hand. Which statement is true about the forces his two hands exert on each other?

Josh's right hand and left hand exert equal and opposite forces on each other

Josh punches his open left hand with his right hand. Which statement is true about the forces his two hands exert on each other?

Josh's right hand and left hand exert equal and opposite forces on each other.

While sparring, Katie punches Arman in the shoulder. Which statement is true about the forces Katie and Arman exert on each other?

Katie exerts a force on Arman's shoulder and Arman exerts a force on Katie's hand.

A block of mass M is attached to a modified Atwood machine and is accelerated upward at 3a by a constant force 𝐹0 . What is the weight of the block?

Mg

Miguel leans against a wall. Which statement is true about the forces Miguel and the wall exert on each other?

Miguel and the wall exert equal and opposite forces on each other.

Acceleration can be expressed in units of m/s2 or __________.

N/kg

Jack and Luis are pushing on opposite ends of a shopping cart. At the moment, the cart is staying at rest. We know that the forces each person exerts on the cart are equal in magnitude and opposite in direction. What is the reason this must be true?

Newton's second law tells us these two forces must be equal and opposite.

Identical spheres are dropped from a height of 100m above the surfaces of both Planet Xand Planet Y. The position of the spheres as a function of time is recorded as the spheres fall. These data are shown in the graphs above. Which planet exerts a greater gravitational force on the sphere, and what evidence supports this conclusion?

Planet Y, because the slope of the curve increases at a faster rate.

Three boxes are pulled to the left by strings with negligible mass on a horizontal surface, as shown above. The masses of the boxes are LaTeX: m_1,\:m_2,\:𝑚1,𝑚2,and LaTeX: m_3𝑚3, where LaTeX: m_3>m_2>m_1𝑚3>𝑚2>𝑚1. Friction between the boxes and the surface is negligible. The figure below shows force diagrams for each box.

T_B<T_A<F

If you know all of the forces acting on an object and you know the mass of that object, what quantities can you figure out from that information?

The acceleration of the object

A 1500 kg car traveling along a road is hit by a 0.1kgrock that creates a small crack in the car's windshield. Which of the following describes the interaction between the windshield and the rock?

The car exerts a force on the rock, and the rock exerts a force on the car. The two forces are equal in magnitude.

Which of the following is a legitimate way to describe the force between a skydiver and the air she is falling through as the skydiver is falling toward the ground?

The drag force exerted by the air on the skydiver

An object rests on a ramp that is angled at 20º above the horizontal. What direction (relative to the vertical) will the force of gravity point?

The gravitational force will be directed exactly downward, along the vertical.

A spring-loaded launcher has a mass of 0.60 kg and is placed on a platform 1.2 m above the ground. The force of friction is negligible between the platform and the launcher. The launcher fires a 0.30 kg ball that lands a distance D to the right of the platform, as shown in the diagram above. Which of the following explanations is true?

The launcher will fall off the platform and land LaTeX: \frac{D}{2}𝐷2 to the left of the platform because the launcher is twice the mass of the ball.

Blocks A and B are connected by rope 1 and are pulled at constant speed across a rough surface by rope 2, which is attached to block B, as shown. Compare the magnitude of the tensions in ropes 1 and 2.

The magnitude of the tensions in the two ropes will not be equal.

If you could somehow increase the mass of an object, what would happen to the net force on the object?

The net force on an object doesn't depend on the object's mass.

You are standing in an elevator as it starts to move downward, accelerating for a moment. Which of these is true at that moment?

The net force on you changes from zero to downward as the elevator begins accelerating.

Which of the following is a legitimate way to describe the force between a road and a car driving on the road?

The normal force exerted by the road on the car

Consider a car speeding up as it drives along a level road. Which of the following is an action-reaction pair (from Newton's third law)?

The normal force exerted on the car by the road and the downward force exerted on the road by the car.

As you accelerate upward in an elevator, which force exerted on you has the greatest magnitude?

The normal force from the elevator floor pushing up on you

Allison pulls her little brother, Brody, in a sled on a snow-covered path at a constant speed. Which of the following is an action-reaction pair (from Newton's third law)?

The pulling force that Allison exerts on the sled and the pulling force that the sled exerts on Allison.

You are about to check out at the grocery store and you put a box of cereal on the conveyer belt at the register. The cashier turns on the conveyor belt, causing the box of cereal to speed up momentarily. At this moment, what can we say about the frictional force acting on the box of cereal?

There is a static frictional force pointing in the box's direction of motion, parallel to the conveyer belt.

Which of the following statements best describes the force or forces exerted on the puck after it is hit by the stick and slides on the ice?

There is no frictional force exerted on the puck, and the gravitational force and normal force are exerted on the puck and are equal in magnitude.

Which of the following experiments could be used to determine the inertial mass of a block?

Use a spring scale to exert a force on the block. Measure the acceleration of the block and the applied force.

Under which circumstance is a force exerted on an apple by your hand?

When the apple is at rest in your open hand

Under which circumstance is there a force exerted on the apple by your hand?

When you are picking the apple up off of the floor

In general, when a car is driving along a straight road, the force of friction between a car tire and the road _____________.

can point either forward or backward, depending on what the car is doing.

Forces can be expressed in units of __________.

newtons or pounds

An object's mass and weight are _____.

proportional to each other.

A box rests on a table. The normal force exerted by the table on the box is equal in magnitude to the weight of the box and points in the opposite direction. This is because ________________.

the net force on the box is zero and, therefore, the forces must be balanced

Newtons and kilograms are __________.

units for different quantities, and cannot be converted to each other

Two objects, object X and objectY , are held together by a light string and are released from rest near a planet's surface in the orientation that is shown in the figure. Object X has a greater mass than object Y. A graph of the acceleration as a function of time for the system's center of mass is shown for the 4s. The positive direction is considered to be upward. How does the speed of object LaTeX: X\:_{v_x}𝑋𝑣𝑥 compare to that of the system's speed LaTeX: _{v_s}𝑣𝑠 after the objects have fallen for 4s ?

vx = vs

Two identical blocks, block A and block B, are placed on different horizontal surfaces. Block A is initially at rest on a smooth surface, while block B is initially at rest on a rough surface. A constant horizontal force of magnitude LaTeX: F_0F 0 is exerted on each block. After the force has been applied for a time LaTeX: \Delta tΔ t, the speeds of blocks A and B are LaTeX: v_Av A and LaTeX: v_Bv B, respectively. Which of the following claims indicates the correct relation between LaTeX: v_Av A and LaTeX: v_Bv B and provides the best justification for the relation?

v_A>v_Bv A > v B . The forces between the atoms in a block and the atoms in a surface oppose the motion of the block and are greater, on average, for block B.

Allison shoves her brother Brody away from her, causing him to fall down (on to a soft surface because Allison would never want to intentionally hurt Brody :)) Which of the following is an action-reaction pair (from Newton's third law)?

The force from Allison on Brody and the force from Brody on Allison form an action-reaction pair.

Which of these is a valid force that could be exerted on a car racing through narrow city streets?

The force of friction between the road and the car (its tires)

Which of the following is a legitimate way to describe the force between a skydiver and the earth as the skydiver is falling toward the ground?

The force of gravity exerted by the earth on the skydiver

When trying to analyze the forces in a situation we sometimes invent forces that don't actually exist. Which of these forces is NOT a valid force that could be exerted on a sled being pulled along a snowy path by a girl?

The force of motion pushing the sled forward

Blocks A and B have equal masses and are connected by a rope that passes over a frictionless pulley, as shown. At this moment, the system is at rest. Compare the magnitudes of the force of tension exerted on block A and the force of tension exerted on block B.

The force of tension exerted on block A is equal in magnitude to the force of tension exerted on block B.

Blocks A and B have equal masses and are connected by a rope that passes over a frictionless pulley, as shown. At this moment, the system is in motion, with block B moving downward and A moving upward at a constant speed. Compare the magnitudes of the force of tension exerted on block A and the force of tension exerted on block B.

The force of tension exerted on block A is equal in magnitude to the force of tension exerted on block B.

Cortni pulls on a rope that is attached to a large crate. She is pulling the crate along at a constant speed as it slides across rough carpet. How does the magnitude of the force of tension exerted on Cortni compare to the magnitude of the force of tension exerted on the crate?

The force of tension exerted on the crate has the same magnitude as the force of tension exerted on Cortni.

Imagine a car sitting empty in the parking lot. Which of the following is the most complete list of the forces that belong on a free-body diagram (FBD) of the car?

The normal force on your car by the pavement it rests on and the force of gravity on your car by the earth

An object rests on a ramp that is angled at 20º above the horizontal. What direction (relative to the vertical) will the normal force from the ramp point?

The normal force will be directed 20º to the right of vertical.

an object is launched upward at angle LaTeX: \theta_0θ 0 above the horizontal with a speed of LaTeX: v_0v 0. The trajectory and three positions of the object, X, Y, and Z, are shown in the figure. Position X is higher than position Z with respect to the ground, and position Y is at the object's maximum vertical position. Which of the following claims is correct about the system that consists of only the object?

The object's acceleration is the same at positions X, Y, and Z

Floating in deep space, you find yourself at rest next to a small asteroid. You reach out and tap the asteroid with a hammer. What happens to you in this process?

You will briefly accelerate away from the asteroid and then drift away at a constant speed.

Newtons and pounds are __________.

different units for measuring force

Rock X is released from rest at the top of a cliff that is on Earth. A short time later, Rock Y is released from rest from the same location as Rock X. Both rocks fall for several seconds before landing on the ground directly below the cliff. Frictional forces are considered to be negligible. Which of the following graphs best represents the vertical displacement of Rock X as a function of time starting from immediately after the rock is released from rest? Take the positive direction to be downward.

graph that curves Up

Rock X is released from rest at the top of a cliff that is on Earth. A short time later, Rock Y is released from rest from the same location as Rock X. Both rocks fall for several seconds before landing on the ground directly below the cliff. Frictional forces are considered to be negligible. Which of the following graphs correctly shows the vertical velocity of rock X as a function of time? Take the positive direction to be upward.

graph that is negative slope in negative quadrant |\

The two blocks eventually stop and reverse direction. Which of the following graphs best predicts the acceleration of block A as it moves up and down the rough, inclined surface? Assume that the positive direction points down the slope.

graph that looks like |-_ but all on the positive portion

A person is trying to pull a heavy crate across a room with a rope that is attached to the crate, but it doesn't move. The tension in the rope ________________.

is equal at both ends of the rope

Consider a car at rest, parked on level ground. The force of friction between a car tire and the ground _____________________.

is zero