Unit 2.3 Work and Energy

WJEC 2.3 Work and Energy

What is work done

It is a measure of the energy being transferred. It is always measured in Joules (J)

What is the gravitational field strength of the earth

10 n/kg

How can cars increase its efficiency

• Start stop system to reduce energy lost while being stationary

• Lighter material such as carbon fibre to reduce the mass of the car

• More streamlined shapes to reduce the work done by friction forces on the car

• Correctly inflated tyres to reduce the work done by frictional forces

How to find the spring constant (k) in a parallel and series spring

Parallel

k=k1+k2

Series

1/k=1/k1+1/k2

Describe the 3 car safety features

1. Seat Belts

   • It stretches slightly when a large force is applied to them, this slows the passenger down over a long distance during a crash.

   • This means the forces on the passenger during the crash are smaller, so less damage will be done on the passenger.

2. Air Bags

   • It inflate rapidly if there’s a collision, so the passenger will hit the compressible air bag instead of the solid dashboard.

   • This increase the distance that the passenger moves whilst the work is being done to slow them down, which mean less force will be apply on the passenger

3. Crumple Zone

   • It is the area at the front and back of the car which crumple up easily in a collision

   • This increases the distance that the whole car moves while work is being done to slow down the car, this reduces the force on the car and the passenger

What occurs when work is done against frictional forces

A rise in temperature of the object, this is cause by the kinetic energy to be converted into heat energy

Explain the relationship between the force applied and the extension of an elastic object

The extension is directly proportional to the force applied, assuming the limit of proportionality isn’t exceeded

What is meant by the inelastic deformation

A deformation which results in the object being permanently stretched and does not return to its original shape when the force is removed

What is the type of energy being stored in a spring when it is stretched

Elastic potential energy