Question

a body is thrown up with a velocity of 78.4ms^-1 . find how high it rise and how much time it will take to return to its point of projection​

Answer 1

At the maximum height,

v = 0

u + at = 0

u = -at

But in the case of vertical upward motion, a = -g. Then,

u = gt

t = u / g

t = 78.4 / 9.8

t = 8 seconds.

This 8 seconds is required for the body to go to the maximum height, and the body requires 8 seconds more to come back to the point of projection from that maximum height.

Thus, the body requires a total of 16 seconds to return back to the point of projection once it is projected.

And the maximum height is given by,

h = (v² - u²) / 2a

h = u² / 2g

h = 78.4² / (2 × 9.8)

h = 313.6 m