Question 1

A 0.200-kg ball strikes a wall at 20.0 m/s toward the wall and rebounds at 12.0 m/s away from the wall. If the contact time is 60.0 ms, what is the magnitude of the average force exerted by the wall on the ball? Use the impulse-momentum theorem.

Accepted Answer

$$107\ \mathrm{N}$$

Question 2

An object at rest explodes into two fragments. The first fragment has a mass of $$14\ \mathrm{g}$$ and moves at $$48\ \mathrm{m/s} in $$the $$+x$$ direction. The second fragment moves at $$32\ \mathrm{m/s}. $$What is the mass and direction of the second fragment?

Accepted Answer

$$21\ \mathrm{g}$$, -x$ direction

Question 3

A $$14,000\ \mathrm{kg}$$ boxcar moving at $$1.50\ \mathrm{m/s}$$ collides and couples with a stationary $$10,000\ \mathrm{kg}$$ boxcar. What is the speed of the combined cars immediately after the collision?

Accepted Answer

$$0.875\ \mathrm{m/s}$$

Question 4

A $$1000\ \mathrm{kg}$$ car traveling west at $$10.0\ \mathrm{m/s}$$ collides with a $$500\ \mathrm{kg}$$ car traveling south at $$20.0\ \mathrm{m/s}. $$The cars stick together. What is the speed of the wreckage immediately after the collision?

Accepted Answer

$$9.4\ \mathrm{m/s}$$

Question 5

A uniform beam is $$2.0\ \mathrm{m}$$ long. If all forces acting on it are shown, what is the net torque about the center of mass (point C)?

Accepted Answer

$$14\ \mathrm{N \cdot m}$$

Question 6

A uniform disk of mass $$M$$ and radius $$R$$ has a massless cord wrapped around its rim. A block of mass $$m$$ hangs from the cord. If the system is released from rest, what is the acceleration of the block?

Accepted Answer

$$\displaystyle \frac{2mg}{2m+M}$$

Question 7

A potter’s wheel is a stone disk of diameter $$90\ \mathrm{cm}$$ and mass $$120\ \mathrm{kg}. If a$$ $$75\ \mathrm{N}$$ force is applied at the edge for one-eighth of a revolution, what is the final angular speed? (Moment of inertia of a disk: $$I = \frac{1}{2}MR^2$)

Accepted Answer

$$2.1\ \mathrm{rad/s}$$

Question 8

A $$3.0\ \mathrm{m}$$ diameter merry-go-round with rotational inertia $$120\ \mathrm{kg \cdot m^2$}$$ spins at $$0.50\ \mathrm{rev/s}. $$Four $$25\ \mathrm{kg}$$ children sit on the edge. What is the new angular speed?

Accepted Answer

$$1.09\ \mathrm{rad/s}$$

Question 9

A skater with rotational inertia $$5.7\ \mathrm{kg \cdot m^2$} ($$arms outstretched) spins at $$3.0\ \mathrm{rev/s}$$ while holding $$2.5\ \mathrm{kg}$$ weights in each hand, $$76\ \mathrm{cm}$$ from the axis. If he pulls his hands to his chest (rotational inertia $$4.2\ \mathrm{kg \cdot m^2$}$$), what is his new spin rate?

Accepted Answer

$$6.1\ \mathrm{rev/s}$$

Question 10

A $$4.2\ \mathrm{m}$$ beam is supported at its center. A $$65\ \mathrm{kg}$$ worker stands at one end. Where should a $$190\ \mathrm{kg}$$ bucket of concrete be suspended for the beam to be in static equilibrium?

Accepted Answer

$$0.72\ \mathrm{m}$$ from the center$

Question 11

A $$1000\ \mathrm{kg}$$ car moving west at $$10.0\ \mathrm{m/s}$$ collides with a $$500\ \mathrm{kg}$$ car moving south at $$20.0\ \mathrm{m/s}. $$After sticking together, in what direction (relative to the positive x-axis) does the wreckage move?

Accepted Answer

$$225^\circ$$ counterclockwise from the positive x-axis

Question 12

A uniform disk of mass $$M$$ and radius $$R is $$mounted on a fixed axle. A block of mass $$m$$ hangs from a cord wrapped around the rim. What is the angular acceleration $$\alpha of $$the disk as the block descends?

Accepted Answer

$$\displaystyle \frac{2mg}{MR}$$

Question 13

A $$3.0\ \mathrm{m}$$ diameter merry-go-round with rotational inertia $$120\ \mathrm{kg \cdot m^2$}$$ spins at $$0.50\ \mathrm{rev/s}. $$Four $$25\ \mathrm{kg}$$ children sit on the edge. What is the change in kinetic energy after they sit?

Accepted Answer

$$386\ \mathrm{J}$$

Question 14

A uniform beam is $$2.0\ \mathrm{m}$$ long. What is the net torque about point $$P at $$one end, given all forces are shown?

Accepted Answer

$$-13\ \mathrm{N \cdot m}$$

Question 15

A block of mass $$m$$ hangs from a cord wrapped around a uniform disk of mass $$M$$ and radius $$R. $$What is the tension $$T in $$the cord as the block accelerates downward?

Accepted Answer

Question 16

A skater spins with arms outstretched at $$3.0\ \mathrm{rev/s}$$, holding $$2.5\ \mathrm{kg}$$ weights in each hand, $$76\ \mathrm{cm}$$ from the axis. If he pulls his hands in, reducing his rotational inertia from $$5.7\ \mathrm{kg \cdot m^2$} to$$ $$4.2\ \mathrm{kg \cdot m^2$}$$, what principle explains the change in his spin rate?

Accepted Answer

Conservation of angular momentum

College Physics I: Step-by-Step Guidance for Final Exam Review Problems (Chapters 7–9)

Study Guide - Practice Questions

Study Guide - Flashcards