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Flashcards in Car Design and Saftey Deck (22):

When a force acts on an object, it causes a change in [ ]



A larger force means a [ ] change in momentum



If someone's momentum changes [ ] the forces on the body will be very large, and more likely to cause injury therefore...

very quickly
This is why cars are designed with safety features that slow people down over a longer time when they have a crash - the longer it takes for a change in momentum, the smaller the force


If a car crashes it will [ ] very quickly - this means a lot of [ ] energy is converted into other forms of enegry in a [ ] of time, which can be [ ] for the people inside

slow down
short amount


In a crash, there'll be a [ ] momentum over a very short time, so the people in the car experience [ ] that could be fatal

big change in
huge forces


What a cars designed to do in crashes?

Designed to convert the kinetic energy of the car and its passengers in a way that is safest for the occupants. They often do this by increasing the time over which momentum changes happen, which lessens the force on the passengers


State some safety features of cars.

Crumple zones
Seat Belts
Side Impact Bars
Air Bags


Describe how crumple zones work

Crumple zones at the front and back of the car crumple up on impact
1) The car's kinetic energy is converted into other forms of energy by the car body as it changes shape
2) Crumple zones increase the impact time, decreasing the force produced by the change in momentum


Describe how Seat Belts work

Seat belts stretch slightly, increasing the time taken for the wearer to stop. This reduces the forces acting on the chest. Some of the kinetic energy of the wearer is absorbed by the seat belt stretching


Describe how Side Impact Bars work

Side impact bars are strong metal tubes fitted into car door panels. They help direct the kinetic energy of the crash away from the passengers to the other areas of the car such as the crumple zones


Describe how Air Bags work

Air bags also slow you down more gradually and prevent you from hitting hard surfaces inside the car


Brakes do work against the [ ] of the car

kinetic energy


When you apply the brakes to slow down the car, [ ] is done



How do breaks reduce the kinetic energy of a car?

By transferring it into heat (and sound) energy


How does a regenerative breaking system work?

Use the system that drives the vehicle to do the majority of the breaking.
Rather than converting he kinetic energy of the vehicle into heat energy, the brakes put he vehicles motor in reverse. With the motor running backwards, the wheels are slowed
At the same time, the motor acts as an electrical generator, converting kinetic energy into electrical energy that is stored as chemical energy in the vehicles battery.


What's the advantage of a regenerative breaking system?

They store the energy of braking rather than wasting it


Cars have different [ ] ratings



What determines how powerful a car is?

The size and design


Cars: The more powerful an engine is, the more [ ] it transfers from its fuel every [ ], and so the faster its [ ] can be

top speed


What is the rough power output of a small car?
Of a sports car?

Small = 50kW
Sports = 100 kW


Cars are designed to be aerodynamic. What does this mean?

They are shaped in such a way that air flows very easily and smoothly past them, so minimising air resistance


Cars reach their top speed when the [ ] force = the driving force provided by the [ ]. With less [ ] to overcome, the car can reach a higher speed before this happens. Aerodynamic cars therefore have higher [ ]

air resistance
top speeds.