Physics WJEC GCSE Unit 2.3 Work and Energy

Double And Triple

When does “Work Done” occur? what is it?

When a force acts on a body, a measure of Energy transferred

What is Work measured in?

Joules (J)

Whats the equation for Work?

Work = Force x Distance moved.

What happens to energy levels when “work done” takes place?

They stay the same, and can change from one kind to another

1. If a skier has 120000 kJ of Gravitational Potential Energy at the top of a slope, what will he have at the bottom?

He’ll have 120000 kJ of Kinetic energy

A slingshot has 2J of energy when loaded, where will the energy transfer to when released

2J of kinetic energy will transfer to the ball

Whats the equation for kinetic energy?

Kinetic Energy = (Mass x Velocity²) / 2

Whats the equation for Gravitational Potential Energy? (GPE)

GPE = Mass x Gravitational Field Strength x Change in Height

What graph shows the energy stored in a spring?

The area under a force x extension graph

What is a spring constant?

The force required for different individual springs to stretch

What is Elastic Limit?

The amount anything with elasticity can stretch to a maximum

What equation do you use to calculate the Spring Constant?

Force = Spring constant x Extension

What makes transfer of energy Efficient?

If all energy is transferred and not lost to environment or being transferred to other types.

What will realistically happen to the energy of the Skier?

Some of the energy (for example, 40000 kJ) will transfer to friction, the rest to kinetic energy.

What is one of the reasons cars are being made more Efficient?

In order to reduce green house gases and waste less energy

what are 4 ways cars have been changed to reduce losses?

1. Start stop system - Reduce loses when idling

2. Lighter materials - Reduce Mass

3. Streamlining - Shaping car to reduce work done by friction

4. Correctly inflating tyres - reduce work done by friction (done by using a sensor, sensor also used to warn driver when levels are low)

What are 3 safety features of a car?

1. airbags

2. Seatbelts

3. Crumple zones

How do seatbelts work in a crash?

By a loop in the belt sown in, ripping, extending the belts length and the passangers distance to stop. this is why belts are replaced when a car has been in a crash.

how do airbags and crumple zones work?

Airbag

Reduce kinetic energy of passanger and prevent injury and added cushioning

Crumple zones

Car absorbing more energy, reducing kinetic energy transferred to passenger

The longer the distance the work is done over…

The smaller the force will be on the passenger.