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Flashcards in Car Design and Safety Deck (21)
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What happens when a force acts on an object?

It causes a change in momentum


A larger force means a ____ change of momentum ( and so a ____ ____ )

A larger force means a faster change of momentum ( and so a greater acceleration )


What happens to the forces and what are the likely effects if someone's momentum changes very quickly (e.g. in a car crash)?

The forces on the body will be very large, and more likely to cause injury


What are cars designed with to do what?

How does this work?

Safety features which slow people down over a longer time 

The longer it takes for a change in momentum, the smaller the force


'If a car crashes it will slow down very quickly'

Explain the effects of this on energy conversion and people

A lot a kinetic energy is converted into other forms of energy in a short amount of time

This can be dangerous for the people inside


In a crash, there'll be a ____ change in momentum over a ____ ____ time, so the people inside the car experience ____ froces that could be ____

In a crash, there'll be a big change in momentum over a very short time, so the people inside the car experience huge forces that could be fatal


What are cars designed to do with kinetic energy?

Convert the kinetic energy of the car and its passengers in a way that is safest for the car's occupants


Often, how do cars convert kinetic energy in a way that is safest for its passengers?

By increasing the time over which momentum changes happen, which lessens the force on the passengers


Give 4 examples of car safety mechanisms that increase the time of momentum changes and thus lessen the forces felt by passengers

1. Crumple zones

2. Seat belts

3. Side impact bars

4. Air bags


Describe how crumple zones work (4)

Located at front and back of the car and crumple up on impact

KE is converted into other forms of energy as the car changes shape

Increases the impact time

 decreasing the force produced be the change in momentum


Describe how seat belts work (3)

Seat belts stretch slightly

Some fo KE absorbed by seat belt strectching

Increasing time taken for wearer to stop

Reduces forces acting on wearer's chest



Describe what are/ how side impact bars work

Strong metal tubes fitted into car door panels

Help direct the KE of the crash away from pasengers to other parts of the car (e.g. the crumple zones)


Name 2 ways air bags increase car safety

1. Slow you down more gradually, decreasing forces acting on your body and preventing injury

2. Prevent you hitting hard surfaces inside the car


When you apply the brakes to slow down a car what is done?

Work is done


How do brakes reduce the KE of the car?

By transferring it into heat (and sound) energy


Explain how regenerative braking systems work

1. Put vehicle's brakes into reverse. Wheels are slowed by motor running backwards.

2. At same time, motor acts as electric generator converting KE into electrical energy that is stored as chemcal ernegy in the vehicle's battery


What is the advantage of regenerative brakes?

They store the energy of braking rather than wasting it


The more powerful an engine is...

...the more energy it transfers from its fuel every second, and so the faster its top speed can be.


Name the 2 ways cars are designed to reach higher speeds

1. Powerful engines

2. More aerodynamic


Define 'aerodynamic' in terms of cars

Cars shaped so that air flows very smoothly and easily past them, so minimising their air resistance


When do cars reach their top speeds?

(think forces)

When the resistive force (e.g. air resistance)


the driving force provided by the engine