Question

There is a person who throws a coin vertically downward with an initial speed of 11.8 m/s from the roof of a building, 34.0 m above the ground. How long does it take the coin to reach the ground? Answer in s.

Answer 1

Time taken by the coin to reach the ground is 1.69 s

Given:

Initial speed, v = 11.8 m/s

Height of the building, h = 34.0 m

Solution:

Now, from the third eqn of motion:

`v'^(2) = v^(2) + 2gh`

`v'^(2) = 11.8^(2) + 2* 9.8* 34.0 = 805.64`

`v' = √(805.64) = 28.38 m/s`

Now, time taken by the coin to reach the ground is given by eqn (1):

v' = v + gt

`t = (v' - v)/(g) = (28.38 - 11.8)/(9.8) = 1.69 s`