# Motion

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## Speed and Distance-Time Graph

- the speed of an object is:

v = s / t

- the distance - time graph for any object that is:

stationary, is a horizontal line

moving at constant speed, is a straight line that sloped upwards

- the gradient of a distance - time graph for an object represents the object's speed

- the speed equation can be rearranged to give:

s = v t    or    t = s / v

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## Velocity and Acceleration

- velocity is speed in a given direction

- a vector is a physical quantity that has a direction as well as a magnitude,

a scalar is a physical quantity that has a magnitude only and does not have a direction

- the acceleration of an object is:

a = change in velocity / time

- deceleration is the change of velocity per second when an object slows down

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## More about Velocity - Time Graph

- a motion sensor linked to a computer can be used to measure velocity changes

- the gradient of the line on a velocity - time graph represents acceleration

- if a velocity - time gradient is a horizontal line, the acceleration is 0

- a positive gradient on a velocity - time graph represents positive acceleration, a negative gradient represents deceleration

- the area under the line on a velocity - time graph represents distance travelled

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## Analysing Motion Graph

- the speed of an object moving at constant speed is given by the gradient of the line on its distance - time graph

- the acceleration of an object is given by the gradient of the line on its velocity - time graph

- the distance travelled by an object is given by an area under the line on its velocity - time graph

- the speed, at any instant in time, of an object moving at changing speed is given by the gradient of the tangent to the line on its distance - time graph

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