Question

Define acceleration and give it si unit when is acceleration of a body negative give two examples of solution with in which acceleration of the body is negative

Answer 1

Acceleration:

• The rate of change of velocity is called as acceleration.
• Its SI unit is metre/second² (m/s²)

• It is given by the formula:

1. a=dv/dt
2. a=v₂-v₁/t₂-t₁
3. a=Δv/Δt

where

a=acceleration of the body

v=velocity

t=time

Acceleration of a body can be negative if rate of change of velocity is negative .This happens when force acting on the body opposes its motion and tries to decelerate it with time.

Example of such situations are:

1.When we leave a ball to roll by itself on the floor.We see that the frictional force acting on the ball stops the ball finally.This is called as negative acceleration.

2.When a ball is thrown upwards. The time being for which it starts to ascend in the air we see that its velocity continuously decreases.This happens due to the negative acceleration acting on the body by gravity.

Hope this helps.

Answer 2

Acceleration

• It is defined as the rate of change in the velocity of a body with respect to time

In other words,

• a=dv/dt

Units

• SI units is m/s2
• CGS is cm/s2

As discussed above the acceleration of rate of change in velocity (V2-V1/T) .

So when the final velocity is less than the initial velocity then the acceleration is negative and a specific name is given to the negative acceleration that is Retardation.

Example Of Retardation;-

1. A body sliding or rolling on the rough surface
2. A body thrown vertically upward
3. Two like charges came toward
4. Car on applying of the brake

Note:- Frictional Force Is Always Retarding Force