Question

The velocity 'u' of a body moving along a straight line with constant retardation 'a' reduces by 60%. What is the time taken doing so?​

Answer 1

Given:

The velocity 'u' of a body moving along a straight line with constant retardation 'a' reduces by 60%.

To find:

Time taken for this change in velocity.

Calculation:

Since the retardation is said to be constant, we Equation of Kinematics to solve this problem;

Initial velocity = u ,

Final velocity = u - 60%u

=> Final velocity = u (1 - 60%)

=> Final velocity = u (1 - 0.6)

=> Final velocity = 0.4 u.

Applying Equation of Kinematics:

$\therefore \: v = u + (acc. \times t)$

$= > 0.4u = u + ( - a)t$

$= > at = u - 0.4u$

$= > at = 0.6u$

$= > t = \dfrac{0.6u}{a}$

So, final answer is:

$\boxed{ \sf{ \large{ \blue{time \: taken = \dfrac{0.6u}{a} }}}}$