Q. Two trains travelling on the same track are approaching each other with equal speeds of $40ms^{- 1}$. The drivers of the trains begin to decelerate simultaneously when they are just 2 km apart. If the decelerations are both uniform and equal, then the value of deceleration to barely avoid collision should be
A) $0.8ms^{- 2}$
B) $2.1\ ms^{- 2}$
C) 11.0$\ ms^{- 2}$
D) 13.2$\ ms^{- 2}$
Explanation
(a) Let us calculate relative deceleration by considering relative velocity
Using, $v^{2} - u^{2} = 2aS,0^{2} - 80^{2} = 2 \times a \times 2000$
or $a = - \frac{80 \times 80}{4000} = - \frac{64}{40}ms^{- 2} = - 1.6ms^{- 2}$
Deceleration of each train is $\frac{1.6}{2}ms^{- 2}ie,\ 0.8\ ms^{- 2}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.