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

$$v_f = \frac{3 \times 2}{3 + 2} = 1.2\ \mathrm{m/s}$$

Q: A 1 kg mass is attached to a spring with spring constant $$k = 100\ \mathrm{N/m}$$ and compressed by $$0.2\ \mathrm{m}. $$What is the elastic potential energy stored?

$$U = \frac{1}{2}kx^2$ = \frac{1}{2} \times 100 \times (0.2)^2$ = 2\ \mathrm{J}$$

Q: A force of $$10\ \mathrm{N} is $$applied to a box over $$5\ \mathrm{m}$$, but $$3\ \mathrm{N} of $$friction opposes the motion. What is the net work done on the box?

$$W = (10 - 3) \times 5 = 35\ \mathrm{J}$$

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

$$K = \frac{1}{2}mv^2$ = \frac{1}{2} \times 5 \times 9 = 22.5\ \mathrm{J}$$

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 correct?

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 represents the conservation of mechanical energy in the absence of nonconservative forces?

Accepted Answer

$$K_i + U_i = K_f + U_f$$

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

Accepted Answer

$$W = Fd\cos	heta$$

Question 8

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

Accepted Answer

$$v_f = \frac{3 	imes 2}{3 + 2} = 1.2\ \mathrm{m/s}$$

Question 9

Which of the following is true for the center of mass of a system of particles?

Accepted Answer

It moves as if all the mass and external forces are concentrated at that point.

Question 10

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 11

A wheel accelerates from rest with a constant angular acceleration $$\alpha. $$What is its angular velocity after time $$t$$?

Accepted Answer

$$\omega = \alpha t$$

Question 12

Which formula relates linear velocity $$v$$ and angular velocity $$\omega$$ for a point at radius $$r$$ from the axis of rotation?

Accepted Answer

$$v = \omega r$$

Question 13

A 1 kg mass is attached to a spring with spring constant $$k = 100\ \mathrm{N/m}$$ and compressed by $$0.2\ \mathrm{m}. $$What is the elastic potential energy stored?

Accepted Answer

$$U = \frac{1}{2}kx^2$ = \frac{1}{2} 	imes 100 	imes (0.2)^2$ = 2\ \mathrm{J}$$

Question 14

A rotating rigid body has angular velocity $$\omega$$ and moment of inertia $$I. $$What is its rotational kinetic energy?

Accepted Answer

$$K = \frac{1}{2}I\$$omega^2$$

Question 15

A force of $$10\ \mathrm{N} is $$applied to a box over $$5\ \mathrm{m}$$, but $$3\ \mathrm{N} of $$friction opposes the motion. What is the net work done on the box?

Accepted Answer

$$W = (10 - 3) 	imes 5 = 35\ \mathrm{J}$$

Question 16

Which of the following is true for an elastic collision?

Accepted Answer

Both kinetic energy and momentum are conserved.

Question 17

A rod of length $$L$$ and mass $$M$$ rotates about an axis through one end perpendicular to its length. What is its moment of inertia?

Accepted Answer

$$I = \frac{1}{3}ML^2$

Question 18

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

Accepted Answer

$$K = \frac{1}{2}mv^2$ = \frac{1}{2} 	imes 5 	imes 9 = 22.5\ \mathrm{J}$$

Question 19

A system of two particles, one of mass 2 kg at $$(0,0)$$ and one of mass 3 kg at $$(4,0)$$, has its center of mass at:

Accepted Answer

$$(x_{cm}, y_{cm}) = (2.4, 0)$$

Work, Energy, Momentum, and Rotation: Structured Study Notes

스터디 가이드 - 연습 문제

학습 가이드 - 플래시카드