Question

The car is moving with the velocity of 80 m/sec. The driver apply the brakes for 5 sec. to stop it, the retardation pf the car is

a) 400m/s
b) -400m/s
c) 16m/s?
d) -16m/s?​

Answer 1

Answer:

$\boxed{\sf (d) \ -16 \ m/s^2}$

Given:

Initial velocity (u) = 80 m/s

Final velocity (v) = 0 m/s

Time taken (t) = 5 sec

To Find:

Retardation of the car

Explanation:

$\sf From \ 1^{st} \ equation \ of \ motion:$

$\sf \boxed{ \bold{v = u + at}}$

Substituting values of v, u & t in the equation:

$\sf \implies 0 = 80 + a(5)$

$\sf \implies 5a + 80 = 0$

$\sf \implies 5a = - 80$

$\sf \implies a = - \frac{80}{5}$

$\sf \implies a = - 16 \: m/s^2$

So,

Retardation of the car = -16 m/s²