Energy (1)- pt1

Question 1

Finish this sentence: energy is never used up it’s just…

Answer 1

transferred between different energy stores and different objects

Question 2

What are the 8 types of energy stores?

Answer 2

1. thermal energy stores/internal energy stores
2. kinetic energy stores
3. gravitational energy stores
4. Elastic potential energy stores
5. chemical energy stores
6. magnetic energy stores
7. electrostatic energy stores
8. nuclear energy stores

Question 3

How can energy be transferred?

Answer 3

• mechanically (by a force doing work)
• electrically (work done by moving charges)
• by heating
• radiation (eg. Light or sound)

Question 4

Define closed system

Answer 4

Systems where neither matter nor energy can enter or leave

Question 5

What happens when a system changes?

Answer 5

• energy is transferred
• it can be transferred into or away from the system between different objects or between different types of energy store

Question 6

What has happened when a system changes? (System means a single or group of object/s)

Answer 6

Energy is transferred

Question 7

When someone throws a ball up what are the energy transfers?

Answer 7

-chemical energy store (of the persons arm) —-> to the kinetic energy store of the ball and arm

Question 8

Describe the energy transfers when a ball is dropped from a height and accelerates due to gravity?

Answer 8

the gravitational force transfers energy from the balls gravitational potential energy store—-> its kinetic energy store

Question 9

Explain the energy transfer when car brakes are pressed

Answer 9

• the friction between the brakes and wheels transfer energy as it slows down
• energy transfers from the wheels kinetic energy stores —-> the thermal energy store of the surroundings

Question 10

Explain the energy transfers when a car crashes into a stationary object

Answer 10

-energy is transferred from the cars kinetic energy store —-> to
other energy stores: elastic potential and thermal energy stores of the object and the car. And also sound waves in the surroundings

Question 11

Explain what happens when energy is transferred to the kinetic energy stores?

Answer 11

• the object speeds up

- but if it’s transferred away from the kinetic stored it slows down

Question 12

What’s the formula to find kinetic energy?

Answer 12

E (k) = 1/2 mv *2
Kinetic energy (J) = 1/2 mass X velocity *2

Question 13

What energy is transferred when an object is lifted up?

Answer 13

• it causes a transfer of energy to the gravitational potential energy store of the object
• the higher the object the more energy transferred to the store

Question 14

The energy in kinetic energy stores of an object depend on what?

Answer 14

Mass and speed

Question 15

The energy in gravitational potential energy stores of an object depend on what?

Answer 15

Mass, height and strength

Question 16

What’s the formula for gravitational potential energy?

Answer 16

E (p) = mgh

Gravitational potential energy (J) = mass (kg) X gravitational field strength (N/Kg) X height (m)

Question 17

When something falls what is its energy transfer?

Answer 17

Energy from its gravatotional potential energy store is transferred to it’s kinetic energy store

Question 18

How do you find the elastic potential Energy?

Answer 18

Ee = 1/2 k e *2

Elastic potential energy (j) = 1/2 x spring constant (N/m) x extension (m)

Question 19

What’s specific heat capacity?

Answer 19

Is the amount of energy needed to raise the temperature of 1kg of a substance by 1* C

Question 20

How do you find the change in thermal Energy?

Answer 20

Change in E = m c change in temperature

Change im thermal Energy (J) = mass (kg) x specific heat capacity (j/kgC) x temperature change (C)

Question 21

Explain the conservation of energy principle?

Answer 21

Energy can be transferred usefully, stored or dissipated but can never be created or destroyed

Question 22

Define power

Answer 22

The rate of energy transfer

Question 23

What 2 equations are there to find power?

Answer 23

Power (W) = energy transferred (j) / time (s)

Power (W) = work done (j) / time (s)

Question 24

Define conduction

Answer 24

It’s the process where vibrating particles transfer energy to neighbouring particles

Question 25

Conduction mainly occurs in…

Answer 25

Solids

Question 26

If an object has high thermal conductivity what does that mean?

Answer 26

It can transfer energy between their particle quickly

Question 27

Explain in detail how conduction works?

Answer 27

• when energy is transfer by heating it’s transferred to the thermal Energy store
• the particles beging to vibrate due to the heat and so collide more
• the collision cause energy transfer to the kinetic energy stores. This is conduction
• this continues all through the object the transferred to the surroundings

Question 28

Convections occur only in….

Answer 28

Liquids and gases

Question 29

Define convection

Answer 29

It’s where energetic particles move away from hotter to cooler regions

Question 30

Explain in detail how convection works

Answer 30

• energy transfer by heating to the thermal Energy stores
• when heated the particles, in liquids and gases, move faster and the space between particles increase
• this causes density of the region to decrease