AP Physics Unit 2 Dynamics

A force of 8 N is applied to a crate so that it moves at a constant velocity of 1.5 m/s. What is the net force on the crate?

• 1.5 N

• 8 N

• 12N

• 0 N

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NGSS.HS-PS2-1

Is it possible for the normal force to be equal to the gravitational force?

• Yes. If the surface is horizontal and F_g is perpendicular to the surface.

• Yes. If the surface is vertical and F_g is parallel to the surface.

• No. F_N will always be less than F_g

• No. F_g will be less than F_N.

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NGSS.HS-PS2-4

Is it possible for the normal force to be zero?

• Yes. If the surface is horizontal.

• Yes. If the surface is vertical

• No. F_N will always be less than F_g

• No. F_g will be less than F_N.

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NGSS.HS-PS2-1

Is it possible for the object in the diagram to be moving to the right and have this free body diagram?

• Yes. It's possible that the x forces were just left off the diagram.

• Yes. It could be moving at a constant velocity.

• No. The FBD shows that the system is in equilibrium on both the x- and y- axis.

• No. An FBD shows all F.

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NGSS.HS-PS2-1

A force accelerates an object of mass M. The same force applied to a second body produces half the acceleration. What is the mass of the second body?

• 2 M

• 0.5 M

• 3 M

• 4 M

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NGSS.HS-PS2-1

A mass of 15 kg is acted on by two forces, one of which is 15 N due east while the second one is 10 N due north. The acceleration of the mass is

• 1.2 m/s^2, 56.3^o north of east.

• 1.2 m/s², 33.7 ^o north of east.

• 1.67 m/s², 56.3^o north of east.

• 1.67 m/s², 33.7 ^o north of east.

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A ball of mass 2.0 kg is acted on by two forces, $\overrightarrow{F_1}$ given by x-y components (-3.0N, +2.0 N) and $\overrightarrow{F_2}$ given by x-y components (+5.0 N, +3.0 N). The magnitude of the acceleration is _____.

• 5.4 N @ 21.8° N of E

• 2.7 N @ 21.8° N of E

• 2.7 N @ 68.2° N of E

• 5.4 N @ 68.2° N of E

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NGSS.HS-PS2-1

The force needed to accelerate the rover Opportunity on Mars at 1 m/s² in the horizontal direction is ________ the force needed to accelerate the rover while it was undergoing testing on Earth. Ignore air resistance.

• equal to

• less than

• greater than

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NGSS.HS-PS2-1

An inertial reference frame is one in which

• Newton's first law describes the behavior of matter.

• the law of inertia is not applicable.

• there is a great deal of matter.

• the object of interest is traveling in a circular path.

You are riding in an elevator that is in motion. Using a spring balance calibrated in newtons, you notice that a 10.0 kg hanging mass reads 120 N on the scale. What is the acceleration of the elevator?

• 9.8 m/s² downward

• 4.9 m/s² upward

• 2.2 m/s² downward

• 2.2 m/s² upward

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NGSS.HS-PS2-1