Question

A stone is projected vertically upward from some height at 2v. Some Δt later another stone is projected vertically upward at v from the same position. If they reach the initial position at the same time, find v.

Answer 1

I’ll make the following assumptions about this question:

- The stone is thrown on Earth, where gravity is assumed as9.81ms−2∴constant- There is no air resistance

Thus, as there is no air resistance and gravity is constant, the time taken to reach the highest point must equal the time taken to fall back down to the point of projection:

∵t0=t1

andt0+t1=10s

∴t0+t0=10s

∴2t0=10s

∴t0=5s