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Question 1

What is change in energy stores?

Answer 1

Chemical energy stores include fuels, foods, or the chemicals found in batteries. The energy is transferred during chemical reactions.
Kinetic energy stores describe the energy an object has because it is moving.
Gravitational potential energy stores describe the energy stored in an object because of its position, such as an object above the ground.
Elastic potential energy stores describe the energy stored in a springy object when you stretch or squash it.
Thermal energy stores describe the energy a substance has because of its temperature.

Question 2

What are energy transfers?

Answer 2

When an object starts to fall freely, it speeds up as it falls. The force of gravity acting on the object causes energy to be transferred from its gravitational potential energy store to its kinetic energy store.

Question 3

What is conservation of energy?

Answer 3

Energy cannot be created or destroyed.

Question 4

Two ways energy can be stored as?

Answer 4

When a rubber band is stretched, its elastic potential energy store increases
When an object is lifted, its gravitational potential energy store is increased.

Question 5

What energy transfers happen during bungee jumping?

Answer 5

• When the rope is slack, energy is transferred from the gravitational potential energy store to the kinetic energy store as the jumper accelerates towards the ground due to the force of gravity.
• When the rope tightens, it slows the bungee jumper’s fall. This is because the force of the rope reduces the speed of the jumper. The jumper’s kinetic energy store decreases and the rope’s elastic potential energy store increases as the rope stretches. Eventually the jumper comes to a stop - the energy that was originally in the kinetic energy of the jumper has all been transferred into the elastic potential energy store of the rope.
• After reaching the bottom, the rope recoils and pulls the jumper back up. As the jumper rises, the energy in the elastic potential energy store of the rope decreases and the bungee jumper’s kinetic energy store decreases to zero. The bungee jumper’s gravitational potential energy store increases throughout the ascent.

Question 6

What is work done?

Answer 6

Energy transferred = work done

Question 7

What is the equation for work done?

Answer 7

Work done = force applied (F) x distance moved along the line of action of the force (s).

Question 8

What s the equation for gravitational potential energy?

Answer 8

GPE = mass x gravitational potential energy x potential field strength x change in height

Question 9

What is useful energy?

Answer 9

Energy transferred to where it is wanted in the way that is wanted.

Question 10

What is wasted energy?

Answer 10

Energy that isn’t usefully transferred

Question 11

What is the equation for energy?

Answer 11

Efficiency = useful/total

Question 12

What is the useful and the wasted energy in a bulb?

Answer 12

Useful = Light emitted from the glowing filament.
Wasted = Energy transfer from the filament heating the surroundings.

Question 13

What is energy?

Answer 13

The more powerful an appliance is, the faster the rate at which it transfers energy.

Question 14

What are the changes in gravitational potential energy stores?

Answer 14

When an object is moved upwards, the energy in its gravitational potential energy store increases. This increase is equal to the work done on it by the lifting force to overcome the gravitational force on the object.
When an object moves down, the energy in its gravitational potential energy store decreases. This decrease is equal to the work done by the gravitational force acting on it.

Question 15

What does work done depend on for an object?

Answer 15

• How far it is moved vertically(its change of height).

* Its height.

Question 16

What is the equation for gravitational potential energy?

Answer 16

GPE = mass x gravitational field strength x change in height.

Question 17

What is the practical for investigating kinetic energy stored?

Answer 17

The ball is released on a slope from a measured height above the foot of the shape. You can calculate the decrease in its gravitational potential energy store by using the following equation :
Change in gravitational potential energy store = mass x gravitational field strength x change in height
Due to conservation of energy, this decrease in the gravitational potential energy store is matched by an equal increase in its kinetic energy store.
The ball is timed, using light gases, over a measured distance between X and Y after the slope.

Question 18

What is the kinetic energy equation?

Answer 18

1/2 x mass x speed^2

Question 19

What is the elastic potential energy?

Answer 19

1/2 x spring constant x extension^2

Question 20

What is energy for a purpose?

Answer 20

Whenever energy is transferred for a purpose in any system, some of the energy is transferred usefully. The rest is dissipated (spreads out) and may be stored in less useful ways. This energy is described as wasted energy because it is not transferred as useful things. For example, when a jet plane takes off, its engine transfer energy from the chemical store in the fuel. Some of this energy increases increases the kinetic energy and the gravitational potential energy of the plane, which is the useful energy transfer pathway. The rest is wasted energy because some of it heats the plane and the surroundings and some in transferred to the surroundings and some is transferred to the surrounding by sound waves caused by the engine vibrations.

Question 21

What is friction at work?

Answer 21

As you are exercising, energy is transferred to the thermal energy store of your muscles(so you get hot) and to the thermal energy store of the machine by the force you exert to overcome the friction in the machine.

Question 22

What is energy and efficiency?

Answer 22

When you lift an object, energy stored in your muscles is transferred to the gravitational potential energy store of the object. The amount transferred depends on the object’s weight and how high you lift it.

Question 23

What is weight and energy measured in?

Answer 23

Weight is measured in Newton’s (N). The weight of a 1 kilogram object on the Earth’s surface is about 10N.
Energy is measured in Joules (J). The energy needed to lift a weight of 1 newton by a height of 1 metre is equal to 1 joule.

Question 24

What can be done to reduce energy waste?

Answer 24

Machines can be made more efficient by reducing the energy they waste. For example, lubrication is used to reduce friction between moving parts

Question 25

What is energy and power?

Answer 25

The energy you supply to the motor per second is that POWER supplied to it.
The more powerful the lift motor is, the faster it moves a particular load.

Question 26

What is the equation for Power?

Answer 26

Energy transferred to appliance/time taken for energy go be transferred.

Question 27

What is the efficiency and power for any appliance?

Answer 27

Its useful power out (or output power) is the useful energy per second transferred by it.
Its total power in (or input power) is the energy per second supplied to it.

Question 28

What is the equation for efficiency?

Answer 28

Useful power out/total power in (x100)

Question 29

How do you work out wasted power?

Answer 29

Total power in - useful power out