Astone is thrown vertically upward with a speed of 24.0 m/s. (a) how fast is it moving when it is at a height of 13.0 m? (b) how much time is required to reach this height? (c) why are there two answers to (b)?

Explanation:

initial speed, u = 24 m/s

acceleration due to gravity, g = - 9.8 m/s^2

(a) h = 13 m

Let it is moving with velocity v at a height of 13 m.

Use third equation of motion

By substituting the values

v  = 17.9 m/s

(b) Let it takes time t to reach at height 13 m

Use second equation of motion

t = 4.28 second or t = 0.62 second

(c) the value of t = 0.62 second shows that the journey is upward and at t = 4.28 second, the stone is in downward journey.

answer: electrons