Question

A toy car of mass $500g$ travels with a uniform velocity of $25cm$ $s^{-1}$ for $5s$. The brakes are then applied and the car is uniformly retarded and comes to rest in further $10s$. Calculate the force exerted by the brakes.

• A. $2.5\times {10}^{-2}N$
• B. $0.25\times {10}^{-2}N$
• C. $1.25\times {10}^{-2}N$
• D. $6.25\times {10}^{-2}N$

Answer 1

Answer: (C)

$1.25\times {10}^{-2}N$

Given that this toy car has a velocity of 25 cm/sec which is also equal to 0.25 m/sec.Here toy car is retarded confirming it has final velocity 0 m/sec and it came to rest within 10 seconds.We know that acceleration is nothing but rate of change of velocity.
$a=(v-u)/t$
$a=(0-0.25)/10$
$a=-0.025m/s^2$.
Given mass 500g which is also equal to 0.5 Kg.
$F=m\times a$
$F=0.5\times 0.025N$
$F=1.25\times {10}^{-2}$
Hence force applied is $1.25\times {10}^{-2}N$.