Question

A stone is thrown upward from the top of a 59.4m heigh cliff with an upward velocity component of 19.6m/s? How long is this stone in the air?

Answer 1

Answer:

Explanation: For t , ( I have taken u y = 19.6 ms^-1 and h = 58.8 , as it allows for easier calc. with g = 9.8 )

S = ut + 0.5 gt^2

-58.8 = +19.6t - 0.5(9.8)t^2

-58.8 = 19.6 t - 4.9 t^2

dividing by 4.9

-12 = 4t - t^2

t^2 - 4t - 12 = 0

t^2 - 6t + 2t - 12 = 0

(t + 2)(t-6) = 0

so neglecting -2 , t is apprx 6 secs . ( Answer will diff when using the given values )