A man (weighing 827 N) stands on a long railroad flatcar (weighing 2949 N) as it

Question

A man (weighing 827 N) stands on a long railroad flatcar (weighing 2949 N) as it rolls at 16.8 m/s in the positive direction of an x axis, with negligible friction. Then the man runs along the flatcar in the negative x direction at 3.93 m/s relative to the flatcar. What is the resulting increase in the speed of the flatcar?

Two spacemen are floating together with zero speed in a gravity-free region of space. The mass of spaceman A is 120 kg and that of spaceman B is 90 kg. Spaceman A pushes B away from him with B attaining a final speed of 0.5 m/s. The final recoil speed of A is:

Test Bank, Question 09.34

Test Bank, Question 09.34

A ball hits a wall and rebounds with the same speed, as diagrammed below. The changes in the components of the momentum of the ball are:

Explanation / Answer

1)

Wm = 827 N

wC = 2949 N

initial speed of flat car , u = 16.8 m/s

let the final speed of rail car is v

Using conservation of momentum

(2949 + 827) * 16.8 = 2949 *v + (v - 3.93) * 827

solving for v

v = 17.66 m/s

increase in speed of flatcar = 17.66 - 16.8

increase in speed of flatcar = 0.86 m/s

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let the recoil speed of A is vA

Using conservation of momentum

120 * vA - 90 * 0.50 = 0

vA = 0.375 m/s

the final recoil speed of A is 0.375 m/s

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