What is thinking distance?
The time taken for a driver to react
What is the breaking distance?
The time taken for the brakes to make a car stop
How do you find the stopping distance?
Stopping distance = thinking distance + breaking distance
What happens to thinking distance when reaction time increases?
What can affect reaction times?
- being tired
- being ill
- taking drugs or alcohol
What does friction do to vehicles?
Slow them down
How do brakes stop cars?
They cause a lot of friction
What can affect the amount of friction created on a road?
The road being wet or having loose gravel
As the mass of a vehicle increases, what happens to the force needed to decelerate it?
What is momentum?
A measure of how strongly something is moving
What is the equation for calculating momentum?
Momentum(kg m/s) = mass(kg) x velocity (m/s)
What is a conservation of linear momentum?
When the total momentum of both objects is the same after the collision as before the collision
How do seat belts protect people during a car accident?
They stretch to reduce the change of momentum and it therefore reduces the force acting on the passenger
What are some benefits of air bags over seat belts?
They reduce momentum to zero more slowly and so prevent seat belt injuries
How do crumple zones help during car accidents?
These crumple in a specific way to reduce the momentum of the car over a longer period of time
How do you calculate force?
Force (N) = change in momentum (kg m/s) / time taken (s)
F= mv-mu / t
How do you calculate change in momentum?
Final velocity - initial velocity
What is work?
The amount of energy transferred
What is work measured in?
How do you calculate the amount of work done?
Work = force x distance moved E = F x d
What is the equation for calculating power?
Power = work done / time taken P = E / t
How do you calculate the work done of stopping a car?
Breaking force x breaking distance
What is gravitational potential energy?
The energy that is stored because of an object’s position in a gravitational field
How do you calculate gravitational potential energy?
GPE(J) = mass(kg) x gravitational field strength(N/kg) x vertical height(m)
GPE = m x g x h
What is the equation for calculating kinetic energy?
KE (J) = 1/2 x mass(kg) x velocity^2
KE = 1/2 x m x v^2