3.2 Energy

Question 1

Work done?

Answer 1

Work is done when a force causes an object to move through a distance. The relationship between work done, W, force, F, and distance, d, moved in the direction of the force is:
W=Fxd

Question 2

How is energy transferred?

Answer 2

Energy is transferred when work is done. Work done against frictional forces causes energy transfer by heating.

Question 3

Elastic potential energy calculation?

Answer 3

The amount of elastic potential energy stored in a stretched spring (assuming the limit of proportionality has not been exceeded) can be calculated using the equation:
E =½×kxe^2

Question 4

Gravitational potential energy?

Answer 4

An object gains gravitational potential energy when it is raised vertically because work is done against the gravitational force. The relationship between gravitational potential energy, E,, mass, m, gravitational field strength, g, and height, h, is:
Ep =mxgxh

Question 5

Kinetic energy?

Answer 5

The kinetic energy of a moving object depends on its mass and its velocity. The relationship between kinetic energy, 4,, mass, m and velocity, v, is:
Ex= ½×mxv^2

Question 6

when the mass of an object is doubled, if it is travelling at the same speed it will..

Answer 6

when the mass of an object is doubled, if it is travelling at the same speed it will have twice the kinetic energy.

Question 7

an object travelling at twice the speed of another object with the same mass will..

Answer 7

an object travelling at twice the speed of another object with the same mass will have four times the kinetic energy

Question 8

Power?

Answer 8

Power is the rate at which energy is transferred or the rate at which work is done. The relationship between power, P, work done, W, or energy transferred, E, and time, t, is:
P=E/t
And
P=w/t

Question 9

When a system changes…
What/where is a system?

Answer 9

When a system changes, energy is transferred. A system is an object or group of objects.

Question 10

Simple pendulum?

Answer 10

A simple pendulum is an example of oscillating motion and energy is transferred between kinetic energy and gravitational potential energy.

Question 11

What can and can’t happen to energy?

Answer 11

Energy can be transferred usefully, stored or dissipated, but cannot be created or destroyed.

Question 12

What happened when energy is transferred?

Answer 12

When energy is transferred only part of it may be usefully transferred; the rest is dissipated so that it is stored in less useful ways. This energy is often described as being ‘wasted”.

Question 13

What forces dissipate energy?

Answer 13

Friction and air resistance are forces that dissipate energy by heating the surroundings.

Question 14

Efficiency of a device can be calculated by…

Answer 14

The efficiency of a device can be calculated using:
useful energy out
efficiency =__________________(x100%)
Total energy in
And

efficiency = useful power out
————————(×100%)
total power in
Students may be required to calculate efficiency

Question 15

Fuels and what they are suitable for?

Answer 15

Fuels are a useful store of energy; different fuels are suitable for different situations and are selected according to a range of factors, such as ease of storage, energy content and safety.

Question 16

what happens when a fuel is used? Do all fuels have the same Efficiency?

Answer 16

When a fuel is used, some energy is transferred to the surroundings. Some fuels are more efficient than others.

Question 17

energy resources and their impact on society?

Answer 17

There is a range of energy sources used on a national and global scale. Their use has implications for society in terms of factors including renewability and the environmental impacts of extraction, use and disposal.

Question 18

Renewable energy sources?

Answer 18

A range of technologies have been developed to provide energy in a renewable way, such as wave power, solar power and geothermal power.