Yr 9 - P1 - Conservation and dissipation of energy

Question 1

Kinetic energy

Answer 1

The energy stored in moving objects

Question 2

Gravitational potential energy

Answer 2

The energy stored in objects raised above ground

Question 3

Chemical Energy

Answer 3

The energy stored in
fuels, food and batteries

Question 4

Thermal Energy

Answer 4

The energy stored by hot
objects

Question 5

Elastic Potential
Energy

Answer 5

The energy stored by
stretched or squashed
objects

Question 6

System change on a tennis ball being projected upwards?

Answer 6

Decreasing: Kinetic
Increasing: Gravitational

Question 7

System change on a vehicle slowing down?

Answer 7

Decreasing: Kinetic
Increasing: Thermal

Question 8

System change on a battery powered drill turning on?

Answer 8

Decreasing: Chemical
Increasing: Kinetic, Thermal

Question 9

System change on a person sliding down on a zipwire?

Answer 9

Decreasing: Gravitational
Increasing: Kinetic, Thermal

Question 10

What is the unit of work done and other forms of energy?

Answer 10

Joules (J)

Question 11

Equation for work done?

Answer 11

Work done (J) = force(N) x distance(m)
W = F x s

Question 12

Equation for energy?

Answer 12

Energy (J) = power (W) x time (s)
E= P x t

Question 13

Equation for GPE?

Answer 13

GPE (J) = mass (kg) x gravitational field strength (N/kg) x height (m)
Ep = m x g x h

Question 14

Equation for Kinetic Energy?

Answer 14

Kinetic Energy (J) = 1/2 x mass (kg) x speed² (m/s)
Ek = 1/2 x m x v²

Question 15

Equation for Elastic Energy?

Answer 15

Elastic energy (J) = 1/2 x spring constant (N/m) x extension² (m)
Ee = 1/2 x k x e²

Question 16

What is a system?

Answer 16

An object or group of objects

Question 17

What is a closed system?

Answer 17

A system where no energy is added and none can escape (eg the universe)

Question 18

Conservation of energy

Answer 18

In a closed system, energy cannot be created or destroyed. The total energy is constant.

Question 19

What happens to energy in all systems?

Answer 19

Energy is dissipated so that it is stored in less useful ways (wasted energy)

Question 20

Where does dissipated energy usually end up?

Answer 20

As a thermal store in the surroundings

Question 21

How can unwanted energy transfers be reduced?

Answer 21

Lubrication (to reduce friction)
Insulations (to reduce the rate of thermal energy transfer

Question 22

How is power defined?

Answer 22

As the rate of which energy is transferred or at the rate of which work is done

Question 23

What is an energy transfer of 1 joule per second is equal to?

Answer 23

1 watt of power

Question 24

2 motors lift the same mass but one of them has more power.
Which motor will lift the mass quickest?

Answer 24

The one with higher power

Question 25

How can you calculate the efficiency of an energy transfer?

Answer 25

Efficiency = Useful energy output/ total energy input

or
Efficiency = Useful power output/ total power input

Question 26

What is work done

Answer 26

Energy transferred by a force