Work Done And Energy

Question 1

Define work done

Answer 1

Work done = constant force x distance moved in the direction of the force

Work is done when energy is transferred from one form to another.

Question 2

Write the equation used for work done

Answer 2

W = Fs

W = work done (J), F = force (N), s = distance moved in the direction of the force (m)

Question 3

What do the letters in the equation W = Fs stand for?

Answer 3

W = work done (J), F = force (N), s = distance (m)

Units must be in Joules for work, Newtons for force, and meters for distance.

Question 4

Apply the equation W = Fs to the situation shown: direction moving F

Answer 4

W = Fcosθ x s

This equation accounts for the angle θ between the force and the direction of movement.

Question 5

Write the equation used to calculate gravitational potential energy

Answer 5

Delta Ep = mgh

sEp = change in GPE (J), m = mass (kg), g = acceleration due to gravity (9.81 m/s²), h = change in height (m)

Question 6

What do the letters in the equation Delta Ep = mgh stand for?

Answer 6

Delta Ep= change in GPE (J), m = mass (kg), g = acceleration due to gravity (9.81 m/s²), h = change in height (m)

GPE refers to gravitational potential energy.

Question 7

Write the equation used to calculate kinetic energy

Answer 7

Delta Ek = 1/2 mv²

Delta Ek = change in KE (J), m = mass (kg), v = velocity (m/s)

Question 8

What do the letters in the equation delta Ek= 1/2 mv² stand for?

Answer 8

Delta Ek= change in KE (J), m = mass (kg), v = velocity (m/s)

KE refers to kinetic energy.

Question 9

What is the principle of conservation of energy?

Answer 9

Energy cannot be created or destroyed, only changed from one form to another

This principle emphasizes the transformation of energy rather than its creation or annihilation.

Question 10

Write the equation showing work done in terms of change in kinetic energy.

Answer 10

Work done = change in KE

KE stands for kinetic energy.

Question 11

List three equations that can be used to calculate power.

Answer 11

• P = W over t
• P = E over t
• P = Fv

P represents power, W represents work done, E represents energy transferred, F represents force, and v represents velocity.

Question 12

What does the letter ‘P’ stand for in the power equations?

Answer 12

Power (W)

The unit of power is Watts (W).

Question 13

What does the letter ‘W’ stand for in the power equations?

Answer 13

Work done (J)

The unit of work done is Joules (J).

Question 14

What does the letter ‘E’ stand for in the power equations?

Answer 14

Energy transferred (J)

The unit of energy is Joules (J).

Question 15

What is the formula for calculating efficiency?

Answer 15

efficiency = (useful energy output / total energy input) × 100%

Efficiency is a measure of how much useful energy is converted from the total energy input.

Question 16

What two kinds of numbers can efficiency be given as?

Answer 16

Decimal or percentage

Efficiency can be expressed as a decimal fraction or as a percentage by multiplying by 100.

Question 17

Write the equation used to calculate efficiency based on power.

Answer 17

efficiency = (power output / power input) × 100%

This formula relates efficiency to the power output and power input of a system.