AQA GCSE Designing Safety Features(Physics)
Designing safety features
There are many safety features that are used everyday in order to protect us from harm. They are designed to reduce impact forces on us during an accident.
Cars have various safety features such as air bags, seat belts, crumple zones. All of these are designed to reduce impact forces on the passenger of the car, during a collision.
Both equations below are the same. This is because mass x velocity = momentum. The top line of both equations will give momentum, which is then divided by a time period.
If a car is moving along and drives into a brick wall, the car will come to a stop as shown in the diagram below.
There will be a change in momentum because when the car is moving it will have a momentum and when it stops the momentum will be 0 kg m/s.
Any stationary object has a momentum of 0 kg m/s
As the time period for the collision increases, the impact force, F will decrease. Lets see this below.
If the time period is doubled from 0.1 seconds to 0.2 seconds, the impact force is halved from 90,000N to 45,000N.
The idea of having the same change in momentum, but over a longer collision time to reduce impact force is used in many safety devices. Such as:
1.Airbags
2.Seatbelts
3. Gymnasium crash mats
4.Cycle helmets
5. Cushioned sufaces for playgrounds
Remember, it is the same change in momentum, longer collision time, reduced impact force.
Practice Question
1. Explain how seatbelts are designed to protect a car driver during a collision.
2.How does the collision time relate to the impact forces
3. If you are jumping off a wall, why should you bend your knees when you land.
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