Question

Particle A is projected vertically down from top of tower of height 80 m with velocity 15 m/s.
Simultaneously particle B is projected vertically up from ground with velocity 25 m/s then the
position at which they will meet?
(1) 30 m from ground
(2) 30 m from the top
(3) 20 m from ground
20 m from the top​

Answer 1

Answer:

Explanation:

Since gravity works on both the objects in the negative x direction and is a vector, we can neglect the effect of gravity. Now it is much simpler: Particle A moving with 15 m/s in negative x direction and Particle B moving with 25 m/s in positive x direction. So let's bring A to rest by giving vector of 15 m/s in x direction. We have to give it to be also for equilibrium in system. So now A is at rest and B moves at 40 m/s toward A and distance is 80m. So time taken is 2 seconds. Now we know that collision will happen after 2 seconds. Looking at the initial case where A is moving downward and B upward, after 2 seconds B will be at 50 m above ground because 25 x 2 = 50. Therefore objects meet at 50 m above ground = 30 m from the top. Hope you understood.