Question

A stone is thrown vertically upward with a speed of 40 metre per second. The time interval for which particle was above 40 meter from the ground is

Answer 1

u = 40 ms^(-1)

At the highest point, v = 0 ms^(-1).

s = 40 m

We have,

v² = u² + 2as

0 = 1600 + 80a

a = - 20 ms^(-2)

Now,

t = (v - u) / a <= v = u + at

t = (0 - 40) / - 20

t = 2 s