topic 1 - energy: energy changes in a system, and the way energy is stored before and after such changes

Question 1

What is a system?

Answer 1

An object or group of objects.

Question 2

What happens when a system changes?

Answer 2

Energy is transferred.

Question 3

What are the 8 types of energy store?

Answer 3

Chemical, nuclear, kinetic, gravitational potential, elastic potential, magnetic, thermal and electrostatic.

Question 4

What is a closed system?

Answer 4

A system where energy and matter can neither enter nor leave.

Question 5

What are the 4 ways energy can be transferred?

Answer 5

Mechanically, electrically, by heating or by radiation.

Question 6

How does the way energy is transferred change when boiling water in an electric kettle?

Answer 6

Energy is transferred to the water (from the kettle’s heating element) by heating, into the thermal energy store.

Question 7

How does the way energy is transferred change when an object is projected upwards?

Answer 7

The inital force exerted by a person to throw an object upwards does work. It causes an energy transfer from the chemical store of a person’s arm to the kinetic enegry store of the ball and arm.

Question 8

How does the way energy is transferred change when a moving object hits an obstacle?

Answer 8

The normal contact force between the moving object and the obstacle does work. It causes energy to be transferred from the moving object’s kinetic energy store to other energy stores. Some energy might also be rasferred away by sound waves.

Question 9

How does the way energy is transferred change when an object is dropped from a height?

Answer 9

Energy is transferred from the object’s gravitational potential energy store to it’s kinetic energy store.

Question 10

How does the way energy is transferred change when a car slows down?

Answer 10

The friction between a car’s brakes and wheels does work as it slows down. This causes energy to move from the wheel’s kinetic store to the thermal energy store of the surroundings.

Question 11

What store does anything that’s moving have energy in?

Answer 11

Kinetic.

Question 12

What is the word equation for kinetic energy?

Answer 12

kinetic energy = 0.5 x mass x (speed2)

Question 13

What is the symbol for kinetic energy?

Answer 13

Ek

Question 14

What is the symbol for mass?

Answer 14

m

Question 15

What is the symbol for speed?

Answer 15

v

Question 16

What are the units for kinetic energy?

Answer 16

joules (J0

Question 17

What are the units for mass?

Answer 17

grams (g)

Question 18

What are the units for speed?

Answer 18

metres per second (m/s)

Question 19

Whtat is the word equation for gravitational potential energy?

Answer 19

gravitational potential energy = mass x gravitational field strength x height

Question 20

What is the symbol for gravitational potential energy?

Answer 20

gpe OR Ep

Question 21

What is the symbol for gravitational field strength?

Answer 21

g

Question 22

What is the symbol for height?

Answer 22

h

Question 23

What are the units for gravitational potential energy?

Answer 23

joules (J)

Question 24

What are the units for gravitational field strength?

Answer 24

Newtons per kilogram (N/kg)

Question 25

What are the units fore height?

Answer 25

metres (m)

Question 26

For a falling object where there is no air resistance, what is equal to the amount of energy lost from the gpe store?

Answer 26

The amount of energy gained in the kinetic store.

Question 27

What is the word equation for elastic potential energy?

Answer 27

elastic potential energy = 0.5 x spring constant x (extension2)

Question 28

What is the symbol for elastic potential energy?

Answer 28

Ee

Question 29

What is the symbol for spring constant?

Answer 29

k

Question 30

What is the symbol for extension?

Answer 30

e

Question 31

What are the units for elastic potential energy?

Answer 31

joules (J)

Question 32

What are the units for spring constant?

Answer 32

Newtons per metre (N/m)

Question 33

What are the units for extension?

Answer 33

metres (m)

Question 34

What is specific heat capacity?

Answer 34

The amount of energy needed to raise 1kg of a substance by 1 °C

Question 35

What is the word equation that links energy tranferred to specific heat capacity?

Answer 35

change in thermal energy = mass x specific heat capacity x temperature change

Question 36

What is the symbol for change in thermal energy?

Answer 36

∆E

Question 37

What is the symbol for specific heat capacity?

Answer 37

c

Question 38

What is the symbol for temperature change?

Answer 38

∆θ

Question 39

What are the units for change in thermal energy?

Answer 39

joules (J)

Question 40

What are the units for specific heat capacity?

Answer 40

joules per kilogram per degree Celcius (J/kg °C)

Question 41

What are the units for temperature change?

Answer 41

degrees Celcius (°C)

Question 42

What is power defined as?

Answer 42

The rate at which energy is transferred or the rate at which work is done.

Question 43

What are the two word equations for power?

Answer 43

power = energy transferred/time AND power = work done/time

Question 44

What is the symbol for power?

Answer 44

P

Question 45

What is the symbol for energy transferred?

Answer 45

E

Question 46

What is the symbol for time?

Answer 46

t

Question 47

What is the symbol for work done?

Answer 47

W

Question 48

What are the units for power?

Answer 48

watts (W)

Question 49

What are the units for energy transferred?

Answer 49

joules (J)

Question 50

What are the units for time?

Answer 50

seconds (s)

Question 51

What are the units for work done?

Answer 51

joules (J)

Question 52

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

Answer 52

A power of 1 watt.

Question 53

What is an example that illustrates the definition of power?

Answer 53

If two identical cars race along the same straight race track to a finish line the car with the most powerful engine will get there first - it will transfer the same amount of energy in less time.