Question

An object A is dropped from rest from the top of a 30 m high building and at the same moment another object B is projected vertically upwards with an initial speed of 15 m/s from the base of the building. Mass of the object A is 2 kg while mass of the object B is 4 kg. The maximum height above the ground level attained by the center of mass of the A and B system is $(takeg=10m/s^2):$

• A. 15 m
• B. 25 m
• C. 30 m
• D. 35 m

Answer 1

The correct option is A 15 m

The correct answer is A.

Given,

The height of the building $=30m$

Initial speed$15m/s$

Mass of object A and B $2kg,4kg$

$g=10m/s^2$

So,

By using relative displacement $=30m$

Relative acceleration is $0m/s^2$

So, $s=vt$

$t=\frac{s}{v}=\frac{30}{15}=2s$

Now, The maximum height above the ground level attained by the center of mass of the A and B

This is half of the total distance

$\frac{30}{2}=15m$