Work, Energy and Power

Question 1

Define work done.

Answer 1

The energy transferred when a force moves an object over a distance.

Question 2

Equation for work done?

Answer 2

W = f d

Question 3

Define energy.

Answer 3

The capacity to do work.

Question 4

What is the principle of conservation of energy?

Answer 4

• In a closed system, the total energy remains constant.

- Energy cannot be created nor destroyed, only transferred from one form to another.

Question 5

Equation for Ek?

Answer 5

Ek = 1/2 m v2

Question 6

Derive the kinetic energy equation

Answer 6

Use SUVAT. Check Notion for answers.

Question 7

When mass is constant, what is kinetic energy directly proportional to?

Answer 7

Square of the speed

Question 8

When speed is constant, what is kinetic energy directly proportional to?

Answer 8

Mass of object

Question 9

Equation for GPE?

Answer 9

GPE = mgh

Question 10

Derive the GPE equation

Answer 10

Check Notion.

Question 11

When is Ek = GPE valid?

Answer 11

If there are no resistive forces

Question 12

Define power.

Answer 12

The rate of work done.

Question 13

Define 1 W

Answer 13

1 Joule per second

Question 14

Equation for power

Answer 14

P = W / t

Question 15

Derive the equation linking power and motion.

Answer 15

Check Notion.

Question 16

Equation linking power and motion?

Answer 16

P = Fv

Question 17

What conditions must be met to use the power-motion equation?

Answer 17

• Constant force
• Constant speed (a=0)
• Net force is 0 so the driving force must equal resistive forces.

Question 18

Equation for efficiency?

Answer 18

Efficiency = useful energy / total energy X 100