Energy- Energy

Question 1

10 stores of energy are c______, t______, k______, g____________ p_________, e_______ p_________, n______, s____, l____, e_______ and m________.

Answer 1

10 stores of energy are chemical, thermal, kinetic, gravitational potential, elastic potential, nuclear, sound, light, electric and magnetic.

Question 2

The unit of energy is ______ (_)

Answer 2

The unit of energy is Joules (J)

Question 3

Energy can be _________ from one form to another but can’t be _______ or _________ this is called conservation of energy.

Answer 3

Energy can be transferred from one form to another but can’t be created or destroyed this is called conservation of energy.

Question 4

How do you calculate energy input?

Answer 4

Energy input= useful energy + wasted energy

Question 5

______ energy is energy that is not in a useful format that is ___________.

Answer 5

Wasted energy is energy that is not in a useful format that is dissipating.

Question 6

How do you calculate work done?

Answer 6

Work done = force applied x distance moved

Question 7

How do you calculate efficiency?

Answer 7

Efficiency = useful energy transferred ÷ total energy supplied by the device

Question 8

How do you calculate power?

Answer 8

Power = energy transferred to appliance ÷ time taken for the energy to be transferred

Question 9

An energy transfer of 1 Joule per second is equal to a power of _ ____

Answer 9

An energy transfer of 1 Joule per second is equal to a power of 1 Watt

Question 10

what is kinetic energy

Answer 10

energy stored in moving objects

Question 11

what is the equation for kinetic energy

Answer 11

Ek= 0.5 x m x v^2

Question 12

why type of energy is petrol

Answer 12

chemical energy

Question 13

when we stretch a spring we are applying _____ to change the ______ of the spring.
this is what scientists call ‘doing ____’

Answer 13

when we stretch a spring we are applying force to change the length of the spring
this is what scientists call ‘doing work ‘

Question 14

we are putting ______ in to stretch the spring. the stretched spring is storing this energy and we call that energy _______ _________ ______.

Answer 14

we are putting energy in to stretch the spring. the stretched spring is storing this energy and we call that energy elastic potential energy

Question 15

if there is no force on the spring there is also no….?

Answer 15

no force = no extension

Question 16

what is the symbol for extension

Answer 16

lower case (e)

Question 17

true of false?
the extension is directly proportional to the force applied

Answer 17

true
if you were to plot this, you would get a straight line running through 0

Question 18

what happens to the extension if you apply to greater force

Answer 18

the extension is no longer directly proportional to the force
the spring has been stretched beyond the limit of proportionality

Question 19

what is the equation for elastic potential energy

Answer 19

Ee= 0.5 x k x e^2

Question 20

in this equation what does the k stand for

Answer 20

the spring constant

Question 21

in this equation what does the e stand for

Answer 21

the extension

Question 22

what unit is the extension measured in

Answer 22

metres (m)

Question 23

what is gravitational potential energy

Answer 23

the energy stored in an object due to its position above the earths surface

Question 24

how do you calculate gravitational potential energy

Answer 24

Ep= m x g x h

Question 25

what is thermal energy

Answer 25

the energy stored due to an objects temperature

Question 26

what is a system

Answer 26

an object or a group of objects

Question 27

what is a closed system

Answer 27

when no energy can be passed in or out of the system

Question 28

explain the energy transfer in a pendulum

Answer 28

• at the top the mass has the maximum store of gravitational potential energy
• as the pendulum swings the energy is transferred into kinetic energy
• the kinetic energy is highest at the bottom as this is when the mass is moving the quickest
• the kinetic energy store then transfers back to gravitational potential energy at the top of the pendulum

Question 29

what could be a problem with this energy transfer

Answer 29

friction

Question 30

as the pendulum swings where is friction found

Answer 30

• friction in the fixed point
• friction as the pendulum passes through the air particles

Question 31

friction causes energy to be transferred to _______ energy

Answer 31

friction causes energy to be transferred to thermal energy

Question 32

what do scientists call this energy

Answer 32

dissipated energy (wasted energy)

Question 33

what will this ‘wasted’ energy do to the pendulum

Answer 33

cause it to gradually swing with less energy and eventually stop

Question 34

how can you reduce unwanted energy transfers

Answer 34

by reducing friction

Question 35

how can you reduce friction

Answer 35

• using a lubricant such as oil on the fixed point
• remove the air particles from around the pendulum

Question 36

explain the energy transfer for a bungee jumper

Answer 36

1. all energy in the system is gravitational potential energy
2. the jumper falls and the enemy is transferred to kinetic energy
3. as the bungee cord starts to tighten the kinetic energy is at its maximum
4. once the cord is fully extended kinetic energy is at 0 (not moving)
   all energy has been transferred to elastic potential energy
5. the cord recoils and the energy is transferred back to kinetic
6. during ascent the kinetic energy gets transferred into gravitational potential energy
7. top of the ascent all energy is now gravitational

Question 37

why does the jumper never return back to its original position

Answer 37

energy is dissipated as thermal energy

Question 38

why is the energy dissipated

Answer 38

due to friction
- with air particles
- stretching effects in the bungee rope which is not fully elastic