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Speed, Velocity, Acceleration

Quantity Definition
Formula
Unit
Speed change of distance with time
distance 
time
m/s
Velocity change of displacement with time
displacement
time
m/s
Acceleration change of velocity with time
(final velocity - initial velocity)
time
m/s2
 
Distance-Time Graph(Displacement-Time Graph)
Speed-Time Graph (Velocity-Time Graph)
Gradient gives Speed (Velocity)
 
Gradient gives Acceleration
Area under Graph gives Distance
 
 
Common Graphs:
 
Stone thrown up and falling down

As the stone is thrown up, it slows down due to gravity until it stops ( v = 0) at the highest height.

The height reached (blue triangle),
is the same as the distance it falls through on the return journey (red).

The acceleration due to gravity is 10 m/s2
Then v / t = 10 m/s2

This graph is also for stone rolling up a smooth slope.
Stone dropped from a height

As the stone falls, it increases its velocity (by 10m/s every second).

When it hits the ground, it stops (v = 0).

The height from which it was dropped is the area under the graph (blue triangle).

The acceleration due to gravity (10m/s2) is v / t.
Terminal Velocity

When an object falls through the air, it experiences air resistance.
As it falls with increasing speed, the resistance increases, reducing the resultant force on the object.
Force decrease, acceleration decrease.
Acceleration decreases, gradient decreases (Section A).
When the air resistance is equal to the weight, there is no resultant force.
NO force, no acceleration.
No acceleration, DOES NOT mean no movement.
NO acceleration, no change in speed.
So the object continues with the same speed (Section B).
 

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