mmer 2017 Exam 3, Page 4 of 6 (4 points) A linebacker (85 kg)unning running at 4

Question

mmer 2017 Exam 3, Page 4 of 6 (4 points) A linebacker (85 kg)unning running at 4 m/s Enst. Calculate the final speed of the two football players after the collisio at 8 m/s west collides with a quarterback (65 kg) after the collision linebacker and quarterback stick together :55 )18) + (65144) 680 (-260 25 = at 8 m/s North, while the quarterback is the collision funning at 4 m/s East. The linebacker and quarterback again stick together aftet Calculate the final speed of the two football players after the collision in this case. g points) In another play, the linelater is running 6 t 6, (1 bonus point) Calculate the angle of the two football players in the previous question after they collide.

Explanation / Answer

4) We need to consider the conservation of momentum here. Let us consider velocity in East direction is positive

intial total momentum = 85*(-8) + (65*4) = -420

After collision,they stick together. Final momentum = (85+65)*v = 150v

From conservation of momentum, -420=150v

v = -420/150 = -2.8m/s = 2.8 m/s(West)

5)Here we need to consider conservation of momentum in North and East directions separately

North direction:

Intial momentum in North direction = 85*8=680 kg-m/s

Let velocity in North direction after collision be vN

Final momentum = 150*vN

150*vN = 680

vN = 4.533 m/s

East direction:

Intial momentum in East direction = 65*4=260 kg-m/s

Let velocity in East direction after collision be vE

Final momentum = 150*vE

150*vE = 260

vE = 1.733 m/s

Final speed = sqrt(4.5332+1.7332) = 4.85m/s

6)The angle that the two football players make ,measured anticlockwise from East, is = tan-1(vN/vE)

= tan-1(4.533/1.733)

= 69.07o

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