# AQA Physics P2 - Speeding up and Slowing down

key points of speeding up and slowing down

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## Force Between Objects

1. When two objects interact, they always exert equal and opposite forces on each other

2. The unit of force is the newton (N)

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## Resultant Force

1. When an object at the start is at rest, the resultant force is zero the effect on the object it stays at rest

2. When an object at the start is moving, the resultant is moving the effect on the object is the velocity stays the same

3. When an object at the start is moving, the resultant force is non-zero in the same direction as the direction of motion of the object, the effect on the object is it accelerates

4. When an object at the start is moving, the resultant force is non-zero in the opposite direction to the direction of motion of the object, the effect on the object is it decelerates

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## Force and Acceleration

Resultant Force (Newtons, N) =

Mass (Kilograms, kg)

times

Acceleration (metres/second squared)

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1. The thinking distance is the distance travelled by the vehicle in the time it takes the driver to react

2. The braking distance is the distance the vehicle travels under the braking force

3. The stopping distance = the thinking distance + the braking distance

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## Falling Objects

1. The weight of an object is the force of gravity on it

2. An object falling freely accelerates at about 10m/s squared

3. An object falling in a fluid reaches a terminal velocity

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