Q: A 2 kg object is dropped from a height of 10 m. Ignoring air resistance, what is its velocity just before hitting the ground? (Use $$g = 9.8\ \mathrm{m/s^2$}.)$$

$$v = \sqrt{2gh} = \sqrt{2 \times 9.8 \times 10} = 14\ \mathrm{m/s}$$

Q: A 3 kg object moves in a circle of radius 2 m at a constant speed of 5 m/s. What is its kinetic energy?

$$K = \frac{1}{2}mv^2$ = \frac{1}{2} \times 3 \times 25 = 37.5\ \mathrm{J}$$

Q: A 2 kg mass is attached to a spring with spring constant $$k = 100\ \mathrm{N/m}$$ and compressed by 0.1 m. What is the elastic potential energy stored?

$$U = \frac{1}{2}kx^2$ = \frac{1}{2} \times 100 \times (0.1)^2$ = 0.5\ \mathrm{J}$$

Q: A 1 kg ball moving at $$3\ \mathrm{m/s}$$ collides inelastically with a 2 kg ball at rest. What is the final velocity of the combined mass?

$$v = \frac{m_1v_1 + m_2v_2}{m_1$ + m_2$} = \frac{1 \times 3 + 2 \times 0}{1 + 2} = 1\ \mathrm{m/s}$$

Q: A wheel starts from rest and accelerates at $$2\ \mathrm{$$rad/s^2$$}$$ for 5 seconds. What is its angular velocity at $$t = 5\ \mathrm{s}$$?

$$\omega = \$$omega_0$$ + \alpha t = 0 + 2 \times 5 = 10\ \mathrm{rad/s}$$

Q: A 0.2 kg object moves in a circle of radius 0.5 m at 6 m/s. What is its angular momentum about the center?

$$L = mvr = 0.2 \times 6 \times 0.5 = 0.6\ \mathrm{kg\cdot m^2$/s}$$

Q: A 5 kg object is lifted vertically at a constant speed by a force over a distance of 3 m. What is the work done by the force?

$$W = Fd = mgd = 5 \times 9.8 \times 3 = 147\ \mathrm{J}$$

Question 1

A 2 kg object is dropped from a height of 10 m. Ignoring air resistance, what is its velocity just before hitting the ground? (Use $$g = 9.8\ \mathrm{m/s^2$}.)$$

Accepted Answer

$$v = \sqrt{2gh} = \sqrt{2 	imes 9.8 	imes 10} = 14\ \mathrm{m/s}$$

Question 2

Which of the following statements about conservative forces is TRUE?

Accepted Answer

The work done by a conservative force depends only on the initial and final positions.

Question 3

A block slides down a frictionless incline of height $$h. $$What is its speed at the bottom if it starts from rest?

Accepted Answer

$$v = \sqrt{2gh}$$

Question 4

A 0.5 kg ball moving at $$4\ \mathrm{m/s}$$ collides elastically with a stationary 0.5 kg ball. What is the velocity of the first ball after the collision?

Accepted Answer

$$0\ \mathrm{m/s}$$

Question 5

Which equation correctly expresses the Work-Energy Theorem?

Accepted Answer

$$W_{net} = \Delta K$$

Question 6

A car of mass $$m$$ moves at velocity $$v. $$What is its kinetic energy?

Accepted Answer

$$K = \frac{1}{2}mv^2$

Question 7

A 3 kg object moves in a circle of radius 2 m at a constant speed of 5 m/s. What is its kinetic energy?

Accepted Answer

$$K = \frac{1}{2}mv^2$ = \frac{1}{2} 	imes 3 	imes 25 = 37.5\ \mathrm{J}$$

Question 8

Which of the following is NOT conserved in a completely inelastic collision?

Accepted Answer

Kinetic energy

Question 9

A force $$F$$ acts on a particle over a displacement $$d at an $$angle $$	heta to $$the direction of motion. What is the work done?

Accepted Answer

$$W = Fd\cos	heta$$

Question 10

A 2 kg mass is attached to a spring with spring constant $$k = 100\ \mathrm{N/m}$$ and compressed by 0.1 m. What is the elastic potential energy stored?

Accepted Answer

$$U = \frac{1}{2}kx^2$ = \frac{1}{2} 	imes 100 	imes (0.1)^2$ = 0.5\ \mathrm{J}$$

Question 11

A disk of mass $$M$$ and radius $$R$$ rotates about its center. What is its moment of inertia?

Accepted Answer

$$I = \frac{1}{2}MR^2$

Question 12

A rigid body rotates with angular velocity $$\omega. $$What is its rotational kinetic energy?

Accepted Answer

$$K_{rot} = \frac{1}{2}I\$$omega^2$$

Question 13

A 1 kg ball moving at $$3\ \mathrm{m/s}$$ collides inelastically with a 2 kg ball at rest. What is the final velocity of the combined mass?

Accepted Answer

$$v = \frac{m_1v_1 + m_2v_2}{m_1$ + m_2$} = \frac{1 	imes 3 + 2 	imes 0}{1 + 2} = 1\ \mathrm{m/s}$$

Question 14

Which of the following best describes the center of mass of a system?

Accepted Answer

It is the point where the total mass of the system can be considered to be concentrated for translational motion.

Question 15

A wheel starts from rest and accelerates at $$2\ \mathrm{$$rad/s^2$$}$$ for 5 seconds. What is its angular velocity at $$t = 5\ \mathrm{s}$$?

Accepted Answer

$$\omega = \$$omega_0$$ + \alpha t = 0 + 2 	imes 5 = 10\ \mathrm{rad/s}$$

Question 16

Which of the following is a correct application of the parallel axis theorem?

Accepted Answer

$$I = I_{cm} + Md^2$

Question 17

A 0.2 kg object moves in a circle of radius 0.5 m at 6 m/s. What is its angular momentum about the center?

Accepted Answer

$$L = mvr = 0.2 	imes 6 	imes 0.5 = 0.6\ \mathrm{kg\cdot m^2$/s}$$

Question 18

A 5 kg object is lifted vertically at a constant speed by a force over a distance of 3 m. What is the work done by the force?

Accepted Answer

$$W = Fd = mgd = 5 	imes 9.8 	imes 3 = 147\ \mathrm{J}$$

Question 19

A rotating rigid body has a moment of inertia $$I$$ and angular velocity $$\omega. If $$its angular velocity doubles, what happens to its rotational kinetic energy?

Accepted Answer

It increases by a factor of 4.

Work, Energy, Momentum, and Rotation: Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards