P4 - Explaining Motion

abbie__lou
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Mind Map on P4 - Explaining Motion, created by abbie__lou on 05/29/2014.

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abbie__lou
Created by abbie__lou over 5 years ago
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P4 - Explaining Motion
1 Speeding Up and Slowing Down
1.1 A person walking, cars and bicycles have a driving force.
1.1.1 In the case of a car, the driving force is produced by the engine.
1.1.2 The person's muscles provide the driving force for someone walking or cycling.
1.2 However there is also a counter force, caused by friction and air resistance.
1.2.1 which has the effect of making the vehicle slow down or stop.
1.3 If the driving force is bigger than the counter force, the vehicle accelerates
2 Forces and Motion
2.1 If more than one force acts on an object, the forces need to be added, taking the direction into account.
2.1.1 The overall effect of adding all these forces, taking the direction into account, is called the resultant force
2.2 Arrows are used when drawing diagrams of forces.
2.2.1 The size and direction of the arrow represents the size of the force and the direction that it is acting in.
3 Momentum
3.1 Momentum is a measure of the motion of an object.
3.2 The momentum of an object is calculated using the following formula: Momentum = Mass (kg) x Velocity (m/s)
3.3 Change in Momentum
3.3.1 The size of the change in momentum depends on the size of the resultant force and the length of time the force is acting on the object
4 Collisions
4.1 If a car is involved in a collision it comes to a sudden stop
4.1.1 i.e. it undergoes a change in momentum
4.1.1.1 If this change in momentum is spread out over a longer period of time, the average resultant force acting on the car will be smaller
4.1.1.1.1 Example: A car with a mass of 1000kg, travelling at 10m/s has a momentum of 10,000km m/s
4.1.1.1.1.1 If the car is involved in a collision and it comes to a sudden stop, it would experience a change in momentum of 10,000kg m/s
4.1.2 This sudden change in momentum will affect not only the car, but it's passengers.
4.2 All car safety devices, such as seat belts, crumple zones and air bags, are designed to reduce the force of the impact on the human body
4.2.1 They do this by increasing the time of impact
4.3 A crumple zone is an area designed to 'crumple' on impact.
4.3.1 This helps to increase the time during which the car changes momentum
4.3.1.1 i.e. in stead of coming to a immediate halt, there will be a longer time during which the momentum is reduced
4.3.1.1.1 This means that the force exerted on the people inside the car will be reduced, resulting in fewer injuries

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