Question

Define acceleration and state its SI unit for motion along a straight line, when do we consider the acceleration to be

1. positive
2. negative?

Give an example of a body in uniform acceleration.

Answer 1

Acceleration is the rate of change of velocity with respect to time or it is the rate of change of velocity in unit time. It is a vector quantity. The SI unit of acceleration is ms^-2
Acceleration = Change in velocity/time
= (Final velocity – initial velocity)/time
a = `{v-u}/t`

If v > u, then ‘a’ is positive. If the final velocity is greater than the initial velocity, the velocity increase with time, and the value of acceleration is positive.

If v < u, then a is negative. If the final velocity is less than the initial velocity
Example: The motion of a freely falling body and vertically thrown up the body are examples of uniform acceleration.
The motion of a ball rolling down on an inclined plane is another example.