Question

Q.7 A particle is moving with speed v in a straight line. If the particle starts decelerating with an acceleration a and then it achieved same speed after the time

Answer 1

Answer:

$\frac{2v}{a}$

Explanation:

Initial speed of the particle $=v$

The retardation of the particle $=-a$

Let in time t, its velocity will be v again

But since it will be in the opposite direction of v, the sign will be negative

Using the first equation of motion

$\boxed{v=u+at}$

$-v=v-at$

$\implies 2v=at$

$\implies t=\frac{2v}{a}$

Hope this helps.

Answer 2

The particle will achieve same speed after the time after $\dfrac{2v}{a}$.

Explanation:

It is given that,

A particle is moving with speed v in a straight line. The particle starts decelerating with an acceleration a.

Initial speed is u

Retardation is -a

After time t its velocity is equal to -v as it is moving in opposite direction.

Using equation of motion to find time t. So,

$v=u+at\\\\-v=-v+at\\\\2v=at\\\\t=\dfrac{2v}{a}$

So, the particle will achieve same speed after the time after $\dfrac{2v}{a}$.

Learn more,

Kinematics

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