Q: A person pulls a sled of mass 50 kg with a force of 120 N at an angle of $$30^ ext{o} to $$the horizontal for a distance of 5 m. What is the work done by the person on the sled?

$$W = 120 \times 5 \times \cos 30^ ext{o} = 519.6\ \text{J}$$

Q: A box is moved horizontally by a force $$\vec{F}$$ parallel to its displacement $$\Delta \vec{x}. $$Which equation correctly represents the work done?

$$W = F \cdot \Delta x \cdot \cos \theta$$

Q: If a spring with $$k = 80\ \text{N/m} is $$stretched from $$x_A = 0 to$$ $$x_B = 0.04\ \text{m}$$, what is the work done?

$$W = \frac{1}{2} \times 80 \times (0.04)^2$ = 0.064\ \text{J}$$

Q: A car engine delivers 100 hp. How much power is this in watts?

$$100 \times 746 = 74,600\ \text{W}$$

Question 1

A person pulls a sled of mass 50 kg with a force of 120 N at an angle of $$30^	ext{o} to $$the horizontal for a distance of 5 m. What is the work done by the person on the sled?

Accepted Answer

$$W = 120 	imes 5 	imes \cos 30^	ext{o} = 519.6\ 	ext{J}$$

Question 2

Which of the following best describes the energy transfer when cold milk is added to hot coffee?

Accepted Answer

Thermal energy is transferred from the coffee to the milk through heat.

Question 3

A box is moved horizontally by a force $$\vec{F}$$ parallel to its displacement $$\Delta \vec{x}. $$Which equation correctly represents the work done?

Accepted Answer

$$W = F \cdot \Delta x \cdot \cos 	heta$$

Question 4

A person lifts a bucket vertically upward. If the displacement is horizontal, what is the work done by the vertical force?

Accepted Answer

The work is zero.

Question 5

Which force does work on the block in the diagram where $$\vec{F} is $$applied at an angle $$	heta to $$the horizontal?

Accepted Answer

Only the applied force $$\vec{F}$$ does work.

Question 6

A person carries a box vertically upward. What is the work done by gravity during this displacement?

Accepted Answer

$$W = -mg \Delta y$$

Question 7

For a varying force $$F_x$$ acting along the x-axis, how is the work done from $$x_i to$$ $$x_f$$ calculated?

Accepted Answer

By integrating $$F_x$$ over $$x$$ from $$x_i to$$ $$x_f$$

Question 8

A sled is pulled with a force at an angle $$	heta to $$the horizontal. Which component of the force does work?

Accepted Answer

The horizontal component only

Question 9

According to the work-energy theorem, what is the relationship between net work and kinetic energy?

Accepted Answer

$$W_{net} = KE_f - KE_i$$

Question 10

Which of the following is a conservative force?

Accepted Answer

Gravity

Question 11

A book is moved along two different paths on a table. The work done by friction is greater along the longer path. What does this illustrate?

Accepted Answer

Friction is a nonconservative force.

Question 12

The gravitational potential energy of an object of mass $$m at $$height $$y is $$given by:

Accepted Answer

$$PE = mgy$$

Question 13

A diver drops from a board 10 m above water. Neglecting air resistance, what is his speed as he hits the water?

Accepted Answer

$$v = \sqrt{2g \cdot 10}$$

Question 14

According to Hooke’s Law, the force exerted by a spring is:

Accepted Answer

$$F_s = -kx$$

Question 15

The elastic potential energy stored in a spring stretched by $$x is$$:

Accepted Answer

$$PE_s = \frac{1}{2}kx^2$

Question 16

If a spring with $$k = 80\ 	ext{N/m} is $$stretched from $$x_A = 0 to$$ $$x_B = 0.04\ 	ext{m}$$, what is the work done?

Accepted Answer

$$W = \frac{1}{2} 	imes 80 	imes (0.04)^2$ = 0.064\ 	ext{J}$$

Question 17

What is the SI unit of power?

Accepted Answer

Watt (W)

Question 18

A car engine delivers 100 hp. How much power is this in watts?

Accepted Answer

$$100 	imes 746 = 74,600\ 	ext{W}$$

Question 19

Which equation represents the instantaneous power delivered by a force $$\vec{F}$$ acting on an object moving with velocity $$\vec{v}$$?

Accepted Answer

$$P = F \cdot v$$

Chapter 10: Energy and Work – Study Notes

스터디 가이드 - 연습 문제

학습 가이드 - 플래시카드