Question

From the roof of a tall building, a student throws a ball of mass m = 0.2 kg with initial speed v = 30 m/s at an angle of 20 degrees below the horizontal as shown in the figure. The ball is thrown from a height H above the ground. The student measures the ball to be in the air for 5 seconds before it hits the ground. Ignore air resistance.

What is D, the horizontal distance from the building to where the ball hits the ground?

Answer 1

vi_h=vi cos (20)=30 cos(20)=28 m/s
x=xi+vi*t+at^2
xi=0 ,a=0
xi=28*5=140 m