A healthy young man standing at a distance of 7 m from 11.8 m high building sees a kid slipping from the top floor. With what speed (assumed uniform) should he run to catch the kid at the arms height (1.8m)?

Answer

A, B, D

Explanation

At point B (i.e. over 1.8 m from ground), the kid should be caught.
For kid: Initial velocity
`u=0`
Acceleration = 9.8 m/s^2
Distance S= 11.8-1.8=10 m
No S= ut+ 1/2 `at^2`
10=0+ 1/2 (9.8)`t^2`
` t^2`= 10/4.9=2.04
t= 1.42
`` In this time the man has to reach at the bottom of the building
`:. Velocity =S/t=7/1.42= 4.9 m/s`