Answer:
The collision occurs at a height of 1/3 of the total height of cliff.
Explanation:
The situation is represented in the attached figure:
For the stone dropped from top of cliff we have
Initial velocity of drop= 0 m/s.
Now the time at which it attains a velocity of 2v is obtained from first equation of kinematics as
Thus the distance it covers in this time can be calculated using third equation of kinematics as
For the stone thrown upwards the velocity at collision is give as 'v' thus the velocity at which it is thrown upwards can be calculated by first equation of kinematics as
The height over which it changes it's velocity from '3v' to 'v' can be again obtained from third equation of kinematics as
Thus the collision occurs at at a fraction of 1/3 of height.
