Question

A stone is thrown in vertical upward direction under uniform acceleration due to gravity. If the stone is at same height at 1st second and 7th second from ground, then heights at 3rd second and 5th second are?
(a) 5m, 5m
(b) 80m, 5m
(c) 75m, 75m
(d) 80m, 80m​

Answer 1

Answer:

if the stone is at same height at 1st and 7th second then at 4th sec it will be at its highest position where its velocity is 0

so v=u + at

0=u -gt

-u=-10×4

u=40 m/s

so at 3rd sec

s=ut+1/2 at^2

s=40×3 -1/2 ×10×3×3

s=75 m

at 5th sec

s=40×5-1/2×10×5×5

s=75m