Two particles, one of mass m and the other of mass 2m, are projected horizontally towards each other from the same level above the ground with velocities 10 m/s and 5 m/s, respectively. They collide in air and stick to each other. The distance of the combined mass from point A is

Options

A. (a)40 m
B. (b)20 m
C. (c)30 m
D. (d)zero

Answer

A

Explanation

They will fall through the same height say h. Let them collide at a distance x from tower A.
`therefore h=1/2 gt^(2) ........(i)`
`x=5t .......(ii)`
`60-x=10t ...........(iii)`
Solving (ii) and (iii) we get x=20m, t=4 sec, h=89m