P1-Energy Stores And Systems

Question 1

What happens when energy is transferred to an object

Answer 1

When energy is transferred to an object it is transferred to one of its energy stores

Question 2

What are the 8 different energy stores

Answer 2

Kinetic 
Chemical
Gravitational
Elastic
Thermal
Magnetic 
Nuclear 

Kill chemistry get every (periodic) table make them not legal

Question 3

What are the four different energy transfer pathways

Answer 3

Mechanical pathway -(when a force acts and something moves )

Electrical pathway-(When a current flows)

By heating

By radiation

Question 4

What is a system

Answer 4

A system is one or multiple different objects

Question 5

What happens when a system changes

Answer 5

When a system changes energy is transferred. Energy can be transferred into or out of the system , between different objects in a system or between the objects energy stores

Question 6

What happens to the energy in a kettle when the water boils

Answer 6

When the water boils in a kettle energy is transferred to the water from the kettles heating element through the electrical pathway by heating. This transfers energy to the thermal energy store of the water and causes it to increase in temperature

Question 7

How else apart from heating can energy be transferred

Answer 7

Energy can be transferred when work is done.

Work is done when a current flows or a force moves an object

(Work done means the same as energy transferred

Question 8

How is energy transferred when an object is projected upwards

Answer 8

When an object is projected upwards the initial force of the object going upwards causes work to be done. This causes energy to be transferred from the chemical energy store of the persons arm to the kinetic energy store of the object and the arm

Question 9

What happens to energy when a ball is dropped from a height

Answer 9

When a ball is dropped from a height it is accelerated by gravity and the gravitational force does work. This causes energy to be transferred from the gravitational potential store of the ball to the kinetic energy store of the ball .

Question 10

What happens to energy as a car brakes

Answer 10

When a car breaks the friction between the cars breaks and its wheels causes work to be done as it slows down. Energy is transferred from the kinetic energy stores or the wheels to the thermal energy stores of the surroundings

Question 11

What happens to energy in a collision between a car and a stationary object

Answer 11

In a collision between a car and a stationary object the normal contact force between the two objects causes work to be done . This transfers energy from the kinetic energy store of the car to the elastic and thermal energy stores of the object and car body. Some energy may also be transferred away by sound waves

Question 12

How do you calculate the kinetic energy stored in an object

Answer 12

Kinetic energy (j) = 1/2 mass(kg) x speed (m/s)^2

Question 13

How do you calculate the energy in the gravitational potential store of an object

Answer 13

GPE (j) = mass(kg)x height(m)x gravitational field strength(n/m)

Question 14

What happens when an object falls

Answer 14

-When an object falls energy is transferred from the objects gravitational potential energy store to its kinetic energy store

-Without air resistance
Energy lost from the gravitational potential energy store = energy gained in the kinetic energy store

-With air resistance some of the energy is transferred to other stores

Question 15

How do you work out the amount of energy in the elastic potential energy store

Answer 15

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

Ee=1/2ke^2

Question 16

What is the conservation of energy principle

Answer 16

The conservation of energy principle states that energy can be transferred usefully,stored or dissipated but never created or destroyed

Question 17

What is energy dissipation and when does it happen

Answer 17

• When an energy transfer takes place some energy is always transferred to somewhere you dont want it to go. This is called energy dissipation
• Energy dissipation is often called wasted energy as the energy goes to a store that is not useful e.g the thermal energy stores of surrounding

Question 18

What happens to the energy stores in a phone

Answer 18

A mobile phone is a system and when you use it energy is tranferred to the chemical energy store of the battery. Energy is also dissipated in this transfer to the thermal energy store of the phone

Question 19

What happens when energy is transferred in a closed system

Answer 19

When energy is transferred in a closed system energy transfers still occur within the system but there is no overall energy change because no energy leaves the system

Question 20

What is the equation for power

Answer 20

Power(watts)=energy transferred
—————–
Time

Question 21

What is a powerful machine

Answer 21

A powerful machine is a machine that tranfers lots of energy over a small amount of time

If two identical cars raced the one with the more powerful machine would win as it would transfer more energy over less time

Question 22

What is efficiency of an object

Answer 22

The less energy that us wayed in an energy store , the more efficient an object is

An objects efficiency can be improved by lubricating an object,making it more streamlined or insulating an object

Question 23

How do you calculate efficiency

Answer 23

Efficiency = useful output energy transfer
—————————
Total input energy transfer

Question 24

Why is no device (except for electric heaters ) 100% energy efficient

Answer 24

No device is 100% energy efficient as energy is always transferred to wasted sources. The wasted energy is tranferred to the thermal energy store