P1: Conservation and Dissipation of Energy

Question 1

What is a system?

Answer 1

An object or a group of objects (includes air particles)
In a closed system, no energy can enter or leave

Question 2

Name the 5 energy stores:

Answer 2

Kinetic energy
Chemical energy store
Elastic potential energy store
Gravitational potential energy store
Thermal energy store

Question 3

What is a kinetic energy store?

Answer 3

The energy stored in moving objects

Question 4

What is a chemical energy store?

Answer 4

Includes foods or fuels, describes the energy transferred by chemical reactions

Question 5

What is an elastic potential energy store?

Answer 5

The energy stored by an object when it’s stretched or squashed.

Question 6

What is a gravitational potential energy store?

Answer 6

The energy stored in based on the position of an object, in relation to the gravitational field

Question 7

What is a thermal energy store?

Answer 7

The energy store an object has because of its temperature.

Question 8

What is the principle of the conservation of energy?

Answer 8

Energy cannot be created or destroyed.
(It can only be stored and transferred usefully and dissipated)

Question 9

State the equation for Work Done (Energy Transferred)

Answer 9

W = Fs
Work Done = Force applied * Distance moved
(Joules, J) (Newtons, N) along the line of action
(Meters, m)

Question 10

State the equation for the change in an object’s gravitational potential energy store

Answer 10

Change in GPES = Weight * Change in height
(Joules, J) (Newtons, N) (Meters, m)
or
ΔEp = mgΔh
(mass*gravitational field strength = weight)

Question 11

What happens to the gravitational potential energy store of an object when it is moved upwards or downwards?

Answer 11

Upwards - increases
Downwards - decreases

Question 12

State the equation for kinetic energy

Answer 12

Kinetic energy = 1/2 * mass * speed²
(Joules, J) (Kg) (m/s)
Ek = 1/2mv²

Question 13

State the equation for elastic potential energy

Answer 13

Elastic potential energy = 1/2 * spring constant *
(Joules, J) (Newtons per meter, N/m)
extension²
(Meters, m)
Ee = 1/2ke²

Question 14

What is useful energy and wasted energy?

Answer 14

Useful energy - energy that is transferred in the way we want it
Wasted energy - energy not usefully transferred (not in the way we want it)

Question 15

Why can energy be dissipated?

Answer 15

Due to friction with air particles
Bungee jump - The stretching effects of the rope are not fully elastic

Question 16

What are the two types of work done?

Answer 16

Mechanical work - involves a force used to move an object
Electrical work - involves an electrical current transferring energy

Question 17

What is power?

Answer 17

The rate at which work is done or energy is transferred

Question 18

What is the formula for power?

Answer 18

Power (W) = Energy transferred (J) / time (s)
Power (W) = Work done (J) / time (s)

Question 19

What is the formula for efficiency?

Answer 19

Efficiency = Useful output energy transfer / total input energy transfer
Efficiency Useful power output/ total power output
It can be given as either decimal or percentage