A 3 kg mass moving laterally at 5 m/s collides with a 5 kg mass at rest. As a result the 5 kg mass travels at 2 m/s at a 26 angle counterclockwise from the direction of the motion of the initial mass. The 5 kg mass then collides with a 4 kg mass at rest. The 4 kg mass then leaves at 1 m/s at a 30 angle counterclockwise from the direction of motion of the 5 kg mass.(adsbygoogle = window.adsbygoogle || []).push({});

a. Find the final magnitude and direction for the velocity of each of the first 2 two masses.

Does this apply to only the 3 kg and 5 kg mass?

Let us say m1 = 3 kg, m2 = 5 kg, m3 = 4 kg.

Now I am a bit confused since 3 masses and not 2 are involved.

This is how I started:

1st scene

x component: m1v1 = m1v1'*cos(0) + m2v2'*cos(26)

y component: 0 = m1v1'*sin(0) + m2v2'*sin(26)

But I am not sure if my signs are correct. Then from here I was going to add the 2 equations together to determine v1' and then use substitution for v2' . . .

The 2nd scene with m2 and m3 has stumped me. Do I use similar equations like those above but just replace it with the new velocity of m2 (v2' will be v2 now?) and angles (26 for m2 and 30 for m3)?

b. Are these collisions elastic? Why or why not?

Do I count all the collisions separately or will they all be elastic or inelastic?

Basically I have to see if kinetic energy is conserved by calculating the total KE after the collision(s) and comparing it with before the collision(s). But I don't know what to do from here because a collsion follows another collision, and I am totally lost.

Thanks for the help.

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# Homework Help: Collisions and Momentum

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