posted by blah .
In the javelin throw at a track and field event, the javelin is launched at a speed of 25 m/s at an angle of 30.7° above the horizontal. As the javelin travels upward, its velocity points above the horizontal at an angle that decreases as time passes. How much time is required for the angle to be reduced from 35° at launch to 19.2°?
horizontal speed remains constant, u = 25 cos 30.7
Vertical speed = v = 25 sin 30.7 - 9.8 t
tan 19.2 = (25 sin 30.7 -9.8 t)/u