P1 - Conservation and Dissipation of Energy

Question 1

What is the law of conservation of energy?

Answer 1

Energy cannot be created or destroyed.

only changed from one form to another

Question 2

What is dissipation of heat?

Answer 2

Dissipation of heat is when heat energy is spread out to the surroundings.

Question 3

Name all of the types of energy stores.

Answer 3

Kinetic energy, Gravitational potential energy, Elastic potential energy, Nuclear energy, Thermal energy, Electrostatic energy, Magnetic energy

Question 4

Name the energy pathways (energy transfers).

Answer 4

Mechanical, Heating, Radiation, Electrical

Question 5

Give an example of a chemical energy store.

Answer 5

Batteries, fuels, food.

The energy is transferred during chemical reactions.

Question 6

Give an example of a gravitational potential energy store.

Answer 6

Any object raised to a height.

The energy is transferred when the object falls.

Question 7

Give an example of a kinetic energy store.

Answer 7

Any object that is moving.

Question 8

What is work done?

Answer 8

The energy transferred by a force moving something

Question 9

What is the formula for work done?

Answer 9

W, Work done (Joules) = F, Force (Newtons) x D, Distance moved (metres)

W.D. = F x D

Question 10

What is useful energy?

Answer 10

Energy that is transferred to useful stores.

i.e. Energy transferred by a lightbulb in the form of light energy.

Question 11

What is wasted energy?

Answer 11

Energy that is transferred to a store that is not useful.

i.e. Energy transferred by a lightbulb to heat the surroundings.

Question 12

What is the formula for GPE, Gravitational Potential Energy?

Answer 12

change in GPE (Joules) = Weight (Newtons) x change in Height (metres)

GPE = W x H
GPE = m g h

Question 13

What is the formula for Weight?

Answer 13

Weight (Newtons) = Mass (kilograms) x Gravitational field strength (N/kg)

W = m x g

Question 14

If an object falls from a height, what energy store decreases?

Answer 14

Gravitational potential energy

Question 15

What energy store does a moving object have?

Answer 15

Kinetic Energy

Question 16

What is the gravitational field strength on Earth?

Answer 16

9.81 N/kg or approximately 10 N/kg

Question 17

What is the equation for Kinetic Energy, K.E.?

Answer 17

Kinetic Energy (Joules) = 1/2 x mass (kg) x speed^2 (m/s)

K.E. = 1/2 m v^2

Question 18

What is the equation for Elastic potential energy?

Answer 18

Elastic P.E. (J) = 1/2 x spring constant (N/m) x extension^2 (m)

E.P.E = 1/2 x c x e

Question 19

What happens to the energy when something is stopped by friction?

Answer 19

It is transferred to heat the surroundings (it is dissipated)

Question 20

What word describes heat lost to the surroundings?

Answer 20

Dissipation

Question 21

What is the equation for efficiency?

Answer 21

Efficiency (%) = Useful energy output (J) / Total energy input (J) x 100%

Question 22

What is the maximum possible efficiency?

Answer 22

100%

Question 23

Define power.

Answer 23

Power is the rate of energy transfer.

A more powerful appliance transfers energy at a higher rate.

Question 24

What is the formula for power?

Answer 24

Power, (Watts) = Energy transferred (Joules) / Time taken for transfer (seconds)

P=E/t

Question 25

What is the unit of power?

Answer 25

Watt, W

Question 26

What is the unit for energy?

Answer 26

Joule, J

Question 27

What is the unit of mass?

Answer 27

Kilogram, kg

Question 28

What is the unit for Force?

Answer 28

Newton, N

Question 29

What is the unit for distance?

Answer 29

Metre, m

Question 30

What is the unit for speed?

Answer 30

metres per second, m/s