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| Question | Answer |
| P3f - Crumple Zones | . |
| Momentum | A moving object has momentum. This is the tendency of the object to keep moving in the same direction. It is difficult to change the direction of movement of an object with a lot of momentum. |
| Calculating momentum | Momentum = mass × velocity Momentum is measured in kilograms metres per second, kg m/s Mass is measured in kilograms, kg Velocity is measured in metres per second, m/s |
| To reduce injuries in a collision, forces should be as small as possible. | Force = Change in Momentum ÷ Time Force is measured in newtons, N Change in momentum is measured in kilograms metres per second, kg m/s Time is measured in seconds, s |
| Spreading the momentum change over a longer time reduces the force. To minimise injury, forces acting on the people in the car during an accident must be minimised. | Force = mass x acceleration |
| Car Safety Features | Modern cars have features that absorb energy when a vehicle stops suddenly. These are: -Brakes that get hot -Crumple Zones that change shape -Seat belts that stretch a little -Air bags that inflate and squash |
| Continue... | On impact: - Crumple zones at the front/rear of the car absorb some of its energy by changing shape or 'crumbling' - Seat belts stretch a little so that some of the person's kinetic energy is converted to elastic energy. - Air bags absorb some of the person's kinetic energy by squashing up around them. Air bags increase the time taken for the head's momentum to reach zero, so reduce the forces on it. |
| Preventing Accidents | Other safety features of cars are designed to reduce the chance of an accident happening. They include: - Anti-lock braking system (ABS) – prevents skidding allowing the driver to remain in control. The vehicle stops more quickly as there's more friction between the road and tyres. -Traction control - prevents skidding while accelerating so the car can quickly escape a dangerous situation. - Safety cage – strengthens the cabin section to protect people in a roll-over accident. |
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