Please show all work!! Thank you!!! 43P. A 2000-kg railroad flatcar, which can m

Question

Please show all work!! Thank you!!!

43P. A 2000-kg railroad flatcar, which can move on the tracks with virtually no friction, is sitting motionless next to a station platform. A 100-kg football player is running along the platform parallel to the tracks at 10 M/s. He jumps Onto the back of the flatcar. (a) What is the speed of the flatcar after he is aboard and at rest on the flatcar? (b) Now he starts to walk. at 0.5 m/s relative to the flatcar, to the front of the car. What is the speed of the flatcar as he walks?

Explanation / Answer

a)
use conservation of momentum
initial momentum = fibnal momentum
m1*v1 = (m1+m2)*vf
100*10 = (100+2000)*vf
1000 = 2100*vf
vf= 0.48 m/s
Answer: 0.48 m/s

b)
Let the speed of flat car be v m/s
centre of mass velocity should still be 0.48 m/s
(m1*0.5 + m2*v) /(m1+m2) = 0.48
(100*0.5 + 2000*v) /(100+2000) = 0.48
(100*0.5 + 2000*v )= 1008
v=0.479 m/s
Answer: 0.479 m/s

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