You (mass 55 kg) are riding your frictionless skateboard (mass 5kg) in a straigh

Question

You (mass 55 kg) are riding your frictionless skateboard (mass 5kg) in a straight line at a speed of 4.5 m/s when a bag of flour (2.5kg) is dropped into your arms.
a) what is resulting speed?
b) since the sack was dropped vertically, how can it affect your horizontal motion?
c) if you threw the bag straight up into the air, what would your resulting speed be? explain

My attempt:
a) For an inelastic collision: Vf= (Ma/(Ma+mb))*Vi = 60/60+2.5 * 4.5 = 4.32m/s. Or would it be (2Ma/(ma+mb))*Vai=8.64m/s
b) not sure
c) less than what it was with the bag? Not sure why though

Explanation / Answer

a) You have it right in your first attempt, it's 4.32 m/s. b) This is because momentum is conserved, and since the bag initially has no horizontal speed, you lose horizontal momentum to the bag. c) It would be the same, since if you threw it straight up the bag would keep the same horizontal speed, and so would you.

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