8.6 2-D Collisions Begin Date: 2/5/2018 12:01:00 AM Due Date: 2/13/2018 11:59:00

Question

8.6 2-D Collisions Begin Date: 2/5/2018 12:01:00 AM Due Date: 2/13/2018 11:59:00 PM End Date: 2/11/2019 11:59:00 PM (25%) Problem, 2: Suppose that a 110 kg football player running at 7.5 m/s catches a 0.41 kg ball moving at a speed of 23.5 m/s with his feet off the ground, while both of them are moving horizontally 25% Part (a) Calculate the final speed of the player, in meters per second if the ball and player are initially moving in the same direction. 25% Part (b) Calculate the change in kinetic energy of the system, in Joules, after the player catches the ball. Grade Summary AKE1 Potential 40% sinO coso asin atan acotan) sinh0 coshtanh cotanh) ODegrees O Radians tano acoso Attempts remaining: 2 cotan) (20% per attempt) detailed view 20% 20% 20% I give up Feedback: 5% deduction per Hint Feedback Hints: 5% deduction per hint. Hints remaining feedback. 25% Part (c) Calculate the final speed of the player, in meters per second if the ball and player are initially moving in opposite directions. 25% Part (d) Calculate the change in kinetic energy of the system, in joules, in this case.

Explanation / Answer

(A) Applying momentum conservation,

(110 x 7.5) + (0.41 x 23.5) = (110 + 0.41) vf

vf = 7.56 m/s

(B) Ki = (110 x 7.5^2 / 2) + (0.42 x 23.5^2 / 2)

= 3206.96 J  

Kf = (110 + 0.41) (7.56^2)/2 = 3155.16 J  

delta(K) = Kf - Ki = - 51.8 J  

(C) (110 x 7.5) + (0.41 x -23.5) = (110 + 0.41) vf

vf = 7.38 m/s

(D) Ki = 3206.96 J

Kf = 3010.7 J

delta(K) = - 196.3 J

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