Kinematics Question 377
Question: A car of mass 1000 kg is moving at a speed of 30 m/s. Brakes are applied to bring the car to rest. If the deceleration it’s $ 5m/s^{2} $ the car comes to stop after travelling d m in t s. Then
Options:
A) d = 150, t=5
B) d = 120, t=5
C) d = 180, t=6
D) d = 90, t=6
Show Answer
Answer:
Correct Answer: D
Solution:
Given: mass of car $ m=1000kg $ ; $ ~m=30m/s; $
$ v=0m/s $ Retardation, $ -a=5m/s^{2} $ By equation, $ v^{2}-u^{2}=2as $
$ 0-{{( 30 )}^{2}}=-2\times 5\times d $
$ \therefore d=\frac{900}{10}=90m $
$ \text{and a=}\frac{v-u}{t}\therefore t=\frac{v-u}{a}=\frac{0-30}{-5}=6s $
