Question

03: When a car driver travelling at a speed of 10 m/s applies breaks and brings the
car to rest in 20 seconds, then the retardation will be.
a) 2 m/s²
b) -2 m/s²
c) -0.5 m/s²​

Answer 1

Given that ,

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

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

Thus ,

$\sf \Rightarrow 0 = 10 + 20a \\ \\ \sf \Rightarrow 20a = - 10 \\ \\ \sf \Rightarrow a = \frac{ - 10}{20} \\ \\ \sf \Rightarrow a = - 0.5 \: \: m/ {s}^{2}$

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

Answer 2

Given:-

• Initial velocity of car =10m/s

• Final velocity =0m/s

• Time taken =20s

To Find:-

• Retardation of car.

Solution :-

By using 1st equation of motion.

➦ v =u +at

➭ 0 = 10+ a×20

➭a = -10/20

➭ a = -0.5m/s²

∴The retardation of car is 0.5m/s²