Let v = the launch velocity.
Because the launch angle is 40° (with the horizontal), the initial vertical velocity is
v* sin(40°) = 0.6428v m/s.
Assume g = 9.8 m/s² and ignore air resistance.
At maximum height, the vertical velocity is zero.
Because the maximum vertical height is 10 m, therefore
(0.6428v m/s)² - 2*(9.8 m/s²)(10 m) = 0
0.4132v² = 196
v = 21.78 m/s
Answer: 21.8 m/s (nearest tenth)
