Crumpling zones Flashcards
1
Q
Momentum Formula
A
momentum = mass x velocity
2
Q
Unit for momentum
A
kgm/s
3
Q
What are the safety features that modern cars have that absorb energy when a vehicle stops?
A
- Brakes that get hot.
- Crumple zones that change shape.
- Seat belts that stretch a little.
- Air bags that inflate and squash.
4
Q
On impact
A
- Crumple zones at the front and rear of the car absorb some of its energy by changing shape or crumpling.
- Seat belts stretch a little so that some of the persons kinetic energy is converted to elastic energy.
- Airbags absorb some of the person’s kinetic energy by squashing up around them.
5
Q
All these safety features:
A
- Absorb energy
- change shape
- reduce injuries
- reduce momentum to zero slowly, therefore reducing the force of the occupants.
6
Q
Some people don’t wear like wearing seat belts because:
A
- There is a risk of chest injury
- They may be trapped in a fire
- Drivers may be encouraged to drive less carefully because they know they have protection from seatbelts.
7
Q
Despite computer modelling…
A
Crash tests using real vehicles and dummies provide more safety information.e
8
Q
What is the primary safety feature of a car?
A
- ABS brakes are a primary safety feature which helps to prevent a crash.
- In the ABS system, wheel-speed sensors send information to a computer about the rotational speed of the wheels. The computer controls the pressure to the brakes, via a pump, to prevent the wheels locking up. This increases the braking force before the wheels start to skid.
9
Q
Kinetic enegy lost equals
A
- kinetic enegy lost = work done by the brakes
- ½mv2 = Fd (D = braking distance)
10
Q
If F increases
A
The braking distance (d) decreases.
11
Q
Other primary safety features include:
A
- Cruise control which stops a driver become tired on a long journey and pressing harder on the accelerator.
- Electric windows and paddle shift controls which allow the driver to concentrate on the road.
