## Tuesday, October 20, 2009

### The Equation of linear motion

The equations of linear motion is apply to bodies moving linearly with uniform acceleration .
There are 5 variables in the equation
v = final velocity,
u
= initial velocity,
s = displacement,
a = acceleration,
t
= time

You should be able to solve problems using equation about.

Example :
1. A cyclist accelerates uniformly at 1.2 ms-2 in 10 s from rest. What is his displacement at this time?

Tips:
• Rest mean zero velocity !!
• You need to know 3 variables to find out the required quantities .
Suggested solution
Given;

u = 0 ms-1
a = 1.2 ms-2
t = 10 s
v = ? ( since v is not given you are unable to calculate s using equation 1, 2, 4 and 5)

substitute all given information into equation 3
s= ut+ 1/2 at
2
s= (0) (10) + 1/2 (1.2) (10)2
=60 m (very often, student forget to mention the unit. )

2. A car approaches a traffic light at 15m/s. The traffic light turns red and the driver applies the brakes at the distance of 25 m from the junction and decelerate at 5 ms-2. Can the car come to complete stop before reaching the stop line at the traffic light? (ans : yes)

Tips:
• remember to insert the negative sign (-) for decelerate