4.1.1.1 Energy stores and system

What is a system

An object or group of objects

When a system changes, energy is transferred,way energy is stored also changes

Types of energy stores

Thermal -heat energy

Kinetic- movement

Gravitational potential- position in a gravitational field

Elastic-held in an already stretched spring

Magnetic energy-

Electrostatic

Nuclear

Chemical- chemical bonds

Transferring energy stores

Mechanically

Heating

Electrically

Radiation- light or sound

Open system

Matter of the system can exchange energy with the outside world

Can lose or gain energy as it interacts with the outside worlD

Closed system

Neither matter or energy can enter or leave

The net change in the total energy of a closed system is always 0

Boiling water in a kettle

Electrical energy from the plug is electrically transferred to the thermal energy store of the kettle’s heating element (flow of electricity warms the metal heating element)

The heating element transfers the energy to the waters thermal energy store

Ball rolling and hitting a wall

System is moving ball

When it hits the wall,(some of)the kinetic energy is transferred as sound

types of work done

Mechanical, electrical

Mechanical work done

force to move an object

Electrical work done

When current flows

Energy required to overcome the resistance in the wires of a circuit

Vehicle slowing down

System is vehicle moving

When it slows down, kinetic transfers to thermal due to friction between wheels and brakes

A collision between a car and a stationary object

In a collision between a car and a stationary object, the normal contact force between the car and the object does work. Its causes energy to be transferred from the car is kinetic energy store to other energy stores

Eg. the. Elastic potential and thermal energy stores of the objects in the car body. Some energy might also be transferred away by soundwaves.

Ball thrown upwards

The initial force exerted by a person to throw a ball upwards does work. It causes an energy transfer from the chemical energy store of the persons arm to the kinetic energy of the ball and armed.

A ball dropped

A ball dropped from a height is accelerated by gravity. Gravitational force does work. It causes energy to be transferred from the ball is gravitational potential energy store to its kinetic energy store.