Question

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Answer 1

you need him, @douglaswinslowcooper

Answer 2

Thanks for vote of confidence. Force = change in momentum / time

Force x distance gives you work.
Force times time gives you impulse, which gives you change in momentum (mv).

from the graph, it looks as though the major or only contribution to the
product of force x time is f = about 22 and time = 4.5-0.5 = 4 s.
The impulse seems to be (22)(4) = 88 N-s so this is the change in momentum

If the cart has a mass of m and is moving at v = 10 m/s,
then m (10) = 88
m = 8.8 kg approx.

You may read the graph better than I and have a number a bit different from my F=22N.

Answer 3

Away you go! I'm to bed soon.

Answer 4

N-s is Newton-seconds, a set of units for impulse = (force,N)(time,s)

Answer 5

The - here means "times," like foot-pounds