Speed and Velocity

SPEED 

Is the distance travelled per unit time 

OR 

Is the rate of distance travelled

 The SI-unit of speed is Metre per second (m/s or ms^-1) 

Example 

A man travel at distance of 120 m in 1.2 minutes. Calculate his speed

Solution

Data given

Distance (s) = 120 m

Time (t) = 1.2 minutes

Speed (v) = ?

Firstly, convert 1.2 minutes into seconds

The speed of man = 1.67 m/s

VELOCITY

Is the displacement travelled per unit time

OR

Is the rate of displacement travelled

The SI-unit of velocity is Metre per second (m/s or ms^-1)

Example

A car travelling a displacement of 40 Km in 0.6 minutes. Determine the velocity of the car in SI-unit.

Solution

Data given

Displacement (s) = 40 m

Time (t) = 0.6 minutes

Velocity (v) = ?

Firstly, convert 0.6 minutes into seconds

Secondly, convert 40 Km into metres

The velocity of man = 1111 m/s

Alternative method

Firstly, convert 0.6 minutes into hours

Then convert 4000 Km/h into m/s

The velocity of the car = 1111 m/s

DISPLACEMENT – TIME GRAPHS

The displacement – time graph is the line graph of displacement in the vertical axis against time in the horizontal axis.

Hence the slope in the displacement – time graph represent velocity

Consider the experiment for determining velocity of a walking student of form two as shown in the table below

DISPLACEMENT, s (m)	TIME, t (s)
0	0
4	5
8	8
12	12
16	16

  

 The velocity of the walking student = 1 m/s