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Forces & Motion

The resultant force acting on an object can cause objects to accelerate or decelerate.

resultant force         =          mass           x            acceleration

(newton, N)                 (kilogram, kg)          (metres per second2, m/s2)

distance-time graphs

The gradient of a distance-time graph represents the speed of the object.

Graph for stationary object.

dist time graph 1

Graph for a slow moving object (small gradient).

dist time graph 2

Graph for a fast moving object (steep gradient).

dist time graph 3


Velocity & Speed

Speed example = 5 m/s

Velocity example = 5 m/s North

A speed only has a size like 20 m/s but a speed in a particular direction like 20 m/s left is called a velocity.



The acceleration of an object is measured in metres/second2 ( m/s2).

acceleration = change in velocity

                               time taken for change


velocity-time graphs

Graph for object moving a constant velocity.

vel time graph 1

Graph for object accelerating.

vel time graph 2

Graph for an object decelerating.

vel time graph 3


Acceleration for a velocity-time graph

Finding the gradient of a velocity-time graph  gives you the acceleration of the object. The greater the gradient the greater the acceleration.

Distance travelled from a velocity-time graph

The distance travelled by an object can be found from the area underneath a velocity-time graph.

vel time graph 4

The area underneath this graph is a triangle.

The area of a triangle = 0.5 x  base x height = 0.5 x 10 x 5 = 25m.

The distance travelled by the object is 25m.