Question

The speed of the train is reduced from 36 km per hour to 9 km per hour whilst it travels a distance of 150 metres, if the retardation be uniform, find how much further it will travel before coming to rest.

• A. 10 m
• B. 12 m
• C. 14 m
• D. 16 m

Answer 1

The correct option is A 10 m

initial speed $u=36\times 5/18=10m/s$

final speed $v=9\times 5/18=2.5m/s$

using $v^2=u^2-2as$, with $a=150meter$

we get $a=\frac{100-6.25}{150\times 2}=0.3125m/s^2$

now taking $u=2.5m/s$ and $v=0\left(rest\right)$ with $a=0.3125$ for the second case

we get $s=\frac{6.25}{2\times 0.3125}=10meter$