You throw a stone vertically upward with a speed of 26.0 m/s. (a) How fast is it moving when it reaches a height of 15.0 m? (b) How much time is required to reach this height when it's falling down? a. 19.5 m/s , b. 4.51 s a. 17.9 m/s , b. 0.620 s a. 19.5 m/s , b. 0.800 s a. 17.9 m/s , b. 4.28 s a. 380 m/s , b. 8 s

v = 19.5 m/s

t = 4.51 s

Explanation:

a)

given:

height is 15m from the ground

initial velocity Vi = 26 m/s

acceleration a or g = 9.81 m/s²

formula: Vf² = Vi² + 2aΔy

26² = Vi² + 2 (9.81) 15

Vi = 19.5 m/s

now you can calculate the time by using the equations below:

Δy = 1/2 (Vi + Vf) t

Vf = Vi + a t

Δy = Vi t + 1/2 a t

time must be 4.51 s