GCSE Physics - Forces and Movement

When an unbalanced force acts on an object along the line in which the object is moving, then the object will accelerate (or decelerate if the force acts in the opposite direction to that of the motion of the object)

For a particular object, the bigger the unbalanced force acting on it the bigger the acceleration

If the same force is applied to objects of different mass then the more massive the object the smaller the acceleration will be

force = mass x acceleration    or      F = m x a

The stopping distance of a moving vehicle is the sum of the thinking distance and the braking distance

The thinking distance is the time before the brakes are applied and can be affected by tiredness, drugs and poor visability

The distance travelled while thinking depends on the speed of the vehicle

• The braking distance is the distance travelled by the vehicle after the brakes have been applied
• The braking distance (and therefore the stopping distance) is affected by brake and tyre condition and the condition of the road surface

The mass of the vehicle will also affect its braking distance

weight = mass x accel due to gravity    or     W = m x g

All objects will fall with the same acceleration in the absence of air resistance

Objects falling through liquids and gases experience a drag force which increases with their speed

A falling object reaches terminal velocity because the drag force on the object balances its weight. The drag force will depend on the shape and smoothness of the object.