Question

Q4. When a car driver travelling at a speed of 10m/s applies brakes and brings the car to rest in 20 s, then the retardation will be: a. +2 m/s2 b. -2m/s2 c. -0.5m/s2 d. +0.5m/s2

Answer 1

Given ,

Initial velocity (u) = 10 m/s

Final velocity (v) = 0 m/s

Time (t) = 20 sec

We know that , the Newton's first equation of motion is given by

$\sf \fbox{v = u + at}$

Thus ,

0 = 10 + 20a

20a = -10

a = -0.5 m/s²

$\therefore \sf \underline{The \: retardation \: is - 0.5 \: m/ {s}^{2} }$