A 10 kg block is hanging by a string. How high will it go up if a 2 kg rock going up at 60 m/s hits it and "sticks to it"? (acceleration of 9.8 m/s^2) this has to relate with momentum i think(adsbygoogle = window.adsbygoogle || []).push({});

a 2kg cart and a 4 kg cart are moving together at 4m/s velocity... a spring compressed between them expands rapidly, the front cart continuse at 12m/s in the same direction

a) velocity of 2kg cart after "explosion"

b) if explosion took 0.25s, whats the force of the explosion ( id ont know what mass to use, what acceleration to use)

c) velocity of front cart to acquire in order for second cart to remain stationary after explosion

formulas supposedly used are

F= ma (also is [mass * (change of velocity) ] / change of time )

p=mv

impulse = (F)(change of time)

thanks for any help

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i tried doing them, for the carts question..

a) p=mv

p = (6)(4) 6 kg being total masss of the carts

p = 24 kgm/s

so momentum after is

24 = (4kg . 12 m/s) + (2kg . v) 4kg cart moves at 12 m/s after (its given)

-24 = 2v

v = -12 m/s

so 2kg cart moves -12 m/s after ? i dont know but its a guess

b) if explosion took 0.25s whats the force of it?

well i used the impulse = force * change of time formula..

24 kgm/s = F * 0.25

F = 24 / 0.25

F = 96 N? <--- is that correct? i dont know hope so =D

the last one i dont know because i think the 4kg needs to move really really fast in order for the 2kg cart to not move the opposite way at all.. but no clue how to do it

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# Homework Help: Momentum/velocity questions (very simple)

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