You are on a committee investigating injuries to students partiicipating in spor

Question

You are on a committee investigating injuries to students partiicipating in sports, starting with the high incidence of ankle injuries on the basketball team. Observing the team practice jump shots inspires you to try a small calculation. A student with mass mS=50 kg jumps at h=1.0 m straight up and shoots the mB=0.80-kg basketball at the top of the jump. From the path of the basketball, you estimate that the ball left the hand at 30° from the horizontal at vB=6.0 m/s . To determine the horizontal forces on the ankle, you decide to calculate the student's horizontal velocity when hitting the ground.

Explanation / Answer

This is just like a case of projectile from height with horizontal velocity vB cos 30 = 5.19 m/s

T = sqrt(2 h / g) = sqrt (2 x 1 / 9.8) = .45 sec

V at ground = sqrt (u^2 + g^2 t^2)

V = sqrt (5.19^2 + (9.8^2 x .45^2))

V = 6.81 m/s

Horizontal componant = V cos 30 = 5.89 m/s (amswer)

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