physics
posted by Ashley on .
A 80kg football player leaps straight up into the air (with no horizontal velocity) to catch a pass. He catches the .43kg ball at the peak of his jump, when he is 17.2 inches off the ground. He hits the ground 1.61 inches away from where he leapt. If the ball was moving horizontally when it was caught how fast was the ball traveling?

How long does it take to fall 17.2 inches.
(I assume you are working with an ancient text that uses feet and inches so in your world g = 32 ft/s^2)
17.2 inches /12 in/ft = 1.43 ft
d = 1.43 = (1/2) g t^2
1.43 = 16 t^2
t = .299 seconds to fall
So horizontal speed u took us 1.61 inches in .299 seconds
1.61/12 = u (.299)
so u = .449 ft/second
Call ball speed s
total x momentum of system before catch = momentum of ball = .43 s
so
.43 s = u(80.43) = .449 (80.43)
so
s = 84 ft/s