II Speed, Velocity, Acceleration


Measure of how much distance is passed per time taken.

Unit Speed

m/sm/s or ms1ms^{-1}

Constant Speed

distance=speed×time taken\text{distance} = \text{speed} \times \text{time taken}

Varying Speed

Average speed=Distance travelledTime taken\text{Average speed} = \frac{\text{Distance travelled}}{\text{Time taken}}

Equations and Symbols

s=distance moveds = \text{distance moved}
v=speedv = speed
t=timet = time

s=vts = vt


Y-axis: DistanceDistance
X-axis: TimeTime

For constant speeds the gradient of the straight line is equal to the speed.


Speed in a given direction: Two objects moving in opposing directions at the same speed travel at the same speedspeed, but not with the same velocityvelocity.


The change of velocity per unit of time. A negative value of aa is called decelerationdeceleration.

Acceleration Unit


Constant Acceleration

a=accelerationa = acceleration
s=distance moveds = \text{distance moved}
speeds=u,vspeeds = u, v (with speed changing from uu to vv)

a=vuta = \frac{v-u}{t}

averageaverage speed=12(u+v)speed = \frac 1 2 (u+v)

s=12(u+v)ts = \frac 1 2 (u+v)t


Y-axis: SpeedSpeed
X-axis: TimeTime

Constant acceleration is the gradient of the line relative to the horizontal line at speed uu.

The distance travelled given acceleration and time can be read from the area of the graph. It's equal to the area!


1mile=1.6kilometers1mile = 1.6kilometers