A projectile is fired with an initial velocity of 550 feet p

A projectile is fired with an initial velocity of 550 feet per second at an angle of 70degree with the horizontal. In how many seconds will the projectile reach its maximum altitude? (Round your answer to the nearest tenth of a second.) 24.3 sec 12.8 sec 16.2 sec 21 sec

Solution

equations of projectile

x(t)=550cos(70⁰) t

y(t)=550sin(70⁰) t -16t²

at maximum altitude dy/dt =0

dy/dt =550sin(70⁰) -32t=0

t =(550sin(70⁰))/32

t=16.15

it takes 16.2 sec