Question

A stunt man projects himself horizontal from a height of 60m. He lands 150m away from where he was launched. How fast was he launched?
A.) 54.87 m/s
B.) 43.98 m/s
C.) 47.46 m/s
D.) 42.87 m/s

Answer 1

Answer:

D) 42.87 m/s

Explanation:

First, find the time it takes him to land.  Given in the y direction:

Δy = 60 m

v₀ = 0 m/s

a = 9.8 m/s²

Find: t

Δy = v₀ t + ½ at²

60 m = (0 m/s) t + ½ (9.8 m/s²) t²

t = 3.5 s

Next, find the speed needed to travel the horizontal distance in that time.  Given in the x direction:

Δx = 60 m

a = 0 m/s²

t = 3.5 s

Find: v₀

Δy = v₀ t + ½ at²

150 m = v₀ (3.5 s) + ½ (0 m/s²) (3.5 s)²

v₀ = 42.87 m/s