Question

A fisherman casts his bait toward the river at an angle of 25° above the horizontal. The bait and hook reach a maximum height of What was the initial velocity with which the bait was cast? Assume that the fishing line exerts no appreciable drag force on the bait and hook.

Answer 1

v = v o - g t, where v o is an initial velocity
At the highest point: 0 = v o sin 25° - g t
t = ( v o sin 25° ) / g = 0.4226 v o / 9.81
h max = v o sin 25° · t - g t² / 2
3.2 m = 0.4226 v o · t - 9.81 · t² / 2
3.2 = 9.81 t² - 4.905 t²
3.5 = 4.905 t²
t² = 0.6524
t = √0.6524
t = 0.8 s
v o = ( 0.8 · 9.81 ) : 0.4226
v o = 18.75 m/s = 67.5 km/h
Answer:
The initial velocity was 18.75 m/s.