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Motion graphs tell the story of how an object moves with time.
The graphs can tell the story of an object`s displacement, velocity or acceleration.
An aircraft`s black box records the motion data so that after any accident the motion graphs can be studied.
The graph above shows how the altitude and speed of an aircraft changed with time.
The graph on the right shows that an object travelled at 3 m/s for 10 seconds. In other words it moved with a constant speed of 3 m/s.
Here are some motion graphs you are expected to know at a glance.
The motion graph of this object tells us that its velocity is increasing at a constant rate.
This means that it is accelerating. The objects acceleration can be found by calculating the rate of the velocity.
The rate of velocity is just the gradient of the graph. This gradient of the velocity time graph is the acceleration of the object.
From the graph the object has an acceleration of 0.5 m s-2
In other words the object`s velocity is increasing by 0.5 m s-1 every second.
Click the tv to see how to calculate the acceleration of the object.
Take a look at this velocity time graph.
In this graph the object accelerated at 2 m s-2 for the first two seconds and then moved with a constant velocity of 4 m s-1 for 4 seconds.
Finally the object decelerated at 1 m s-2 for 4 seconds until it came to rest.
Deceleration is now considered as negative acceleration.
So strictly speaking in the last four seconds the objects`s acceleration was - 1m s-2
Click the tv to see how to analyse the velocity time graph
Acceleration time graphs from velocity time graphs
Physicists like to see the accelerations that happened during an objects motion.
Velocity time graph
Corresponding acceleration time graph
Click the tv to see how to convert a velocity time graph into an acceleration time graph.