Question 1

A 0.5 kg ball is struck by a bat, causing its velocity to change from $$-10\ \mathrm{m/s} to$$ $$15\ \mathrm{m/s} in$$ $$0.02\ \mathrm{s}. $$What is the magnitude of the average force exerted by the bat on the ball?

Accepted Answer

$$625\ \mathrm{N}$$

Question 2

A car of mass $$1200\ \mathrm{kg}$$ traveling at $$20\ \mathrm{m/s}$$ collides and sticks to a stationary truck of mass $$1800\ \mathrm{kg}. $$What is the final velocity of the combined mass after the collision?

Accepted Answer

$$12\ \mathrm{m/s}$$

Question 3

Which of the following best describes the Law of Conservation of Momentum in an isolated system?

Accepted Answer

The total momentum before and after an event is equal, provided no external forces act on the system.

Question 4

A $$2\ \mathrm{kg}$$ object moving at $$5\ \mathrm{m/s}$$ collides elastically with a $$3\ \mathrm{kg}$$ object initially at rest. What is the velocity of the $$2\ \mathrm{kg}$$ object after the collision?

Accepted Answer

$$1\ \mathrm{m/s}$$

Question 5

A figure skater spins with angular velocity $$\$$omega_0$$ and moment of inertia I_0$. She pulls her arms in, reducing her moment of inertia to $$\frac{1}{2}$$I_0. $$What is her new angular velocity?

Accepted Answer

$$2\$$omega_0$$

Question 6

A spring with spring constant $$k = 200\ \mathrm{N/m} is $$compressed by $$0.1\ \mathrm{m}. $$What is the elastic potential energy stored in the spring?

Accepted Answer

$$2\ \mathrm{J}$$

Question 7

A $$5\ \mathrm{kg}$$ object is dropped from a height of $$10\ \mathrm{m}. $$Ignoring air resistance, what is its speed just before hitting the ground?

Accepted Answer

$$14\ \mathrm{m/s}$$

Question 8

A $$2\ \mathrm{kg}$$ block slides $$4\ \mathrm{m}$$ across a rough surface with friction force $$5\ \mathrm{N}. $$How much thermal energy is generated?

Accepted Answer

$$20\ \mathrm{J}$$

Question 9

A $$3\ \mathrm{kg}$$ wheel rolls without slipping at $$2\ \mathrm{m/s}. If $$its moment of inertia is $$I = 0.6\ \mathrm{kg\cdot m^2$}$$ and radius $$r = 0.5\ \mathrm{m}$$, what is its total kinetic energy?

Accepted Answer

$$8.4\ \mathrm{J}$$

Question 10

A force of $$10\ \mathrm{N}$$ acts at an angle of $$60^\circ to $$the direction of displacement of $$5\ \mathrm{m}. $$How much work is done?

Accepted Answer

$$25\ \mathrm{J}$$

Question 11

Which of the following statements about energy diagrams is correct?

Accepted Answer

The kinetic energy at any point is the difference between total energy and potential energy.

Question 12

A $$1\ \mathrm{kg}$$ object is attached to a spring ($$k = 100\ \mathrm{N/m}) $$and released from rest at $$x = 0.2\ \mathrm{m}. $$What is its speed as it passes through equilibrium ($$x = 0$$)?

Accepted Answer

$$4\ \mathrm{m/s}$$

Question 13

A $$60\ \mathrm{kg}$$ person climbs a $$5\ \mathrm{m}$$ ladder in $$10\ \mathrm{s}. $$What is the average power output?

Accepted Answer

$$294\ \mathrm{W}$$

Question 14

Which of the following is true for a perfectly inelastic collision?

Accepted Answer

The objects stick together and move with a common velocity after collision.

Question 15

A $$0.2\ \mathrm{kg}$$ ball moving at $$3\ \mathrm{m/s}$$ strikes a wall and rebounds at $$-2\ \mathrm{m/s}. $$What is the impulse delivered to the ball?

Accepted Answer

$$1.0\ \mathrm{kg\cdot m/s}$$

Question 16

A $$2\ \mathrm{kg}$$ object moves in a circle of radius $$0.5\ \mathrm{m} at$$ $$4\ \mathrm{m/s}. $$What is its angular momentum?

Accepted Answer

$$8\ \mathrm{kg\cdot m^2$/s}$$

Question 17

A $$1\ \mathrm{kg}$$ block slides down a $$30^\circ$$ incline ($$h = 2\ \mathrm{m}) $$and reaches the bottom with $$5\ \mathrm{J}$$ less kinetic energy than expected. What is the most likely cause?

Accepted Answer

Friction converted some mechanical energy to thermal energy.

Question 18

Which of the following forces does NO work on an object moving in a circle at constant speed?

Accepted Answer

The centripetal force

Question 19

A $$0.5\ \mathrm{kg}$$ ball is thrown vertically upward with $$20\ \mathrm{J} of $$kinetic energy. Ignoring air resistance, what is the maximum height reached?

Accepted Answer

$$4\ \mathrm{m}$$

Exam 4 Review: Momentum, Energy, Work, and Collisions

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