elastic collision problem

01civicboi · 10-17-2002

I've been busting my brain trying to help my gf with this problem and i can't quite figure it out. I know there are some smart guys on this site

You're mission, if you choose to accept it, is to determine the velocity of the 2 objects after collision.
given info:

Mass 1: 300 g
Velocity 1 (initial) : 7.5 cm/s

Mass 2: 500 g
Velocity 2 (initial) : -5 cm/s

Determine final velocity of each object after an ELASTIC collision.

I calculated the final velocity for an INELASTIC, which made more sense to me.

This is the equation i whipped up: 300(7.5) + 500(-5) = 300*(final velocity 1) + 500*(final velocity 2)

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Boosted2k2 · 10-17-2002

Give me a few minutes and I can probably come up with the answer... I got straight As in physics

AFlyer · 10-17-2002

after a perfectly elastic collision, the velocities of the objects will be exactly the same as they started.

Boosted2k2 · 10-17-2002

I'll keep adding to this: keep checking

m1v1+m2v2 = m1v1f + m2v2f
300g(7.5cm/s) + 500g(-5cm/s) = 300g(v1f) + 500g(v2f)
2250g*cm/s + [-2500g*cm/s] = 300v1f g*cm/s + 500v2f g*cm/s
v1-v2 = vf2-vf1
12.5cm/s +V1f = v2F
-250g*cm/s = 300V1fg*cm/s + 500g(12.5cm/s) + 500gV1f
-250g*cm/s = 800V1fg*cm/s + 6250g*cm/s
-250g*cm/s - 6250g*cm/s = 800V1fg*cm/s
(-6500g*cm/s)/800g*cm/s = V1f = -8.125cm/s
12.5cm/s + V1f = V2f = 12.5cm/s - 8.125cm/s = 4.375cm/s

V1f = -8.125cm/s V2f = 4.375cm/s

theguysmiley · 10-17-2002

I'm so glad I haven't had to deal with physics...my head hurts [IMG]i/expressions/face-icon-small-frown.gif[/IMG]

Smart people!!!

Boilermaker1 · 10-17-2002

Equations for Elastic Collisions:

V1f =((M1-M2)/(M1+M2))V1+((2M2)/(M1+M2)V2

And

V2f =((2M1)/(M1+M2))V1+((M2-M1)/(M1+M2)V2

I get V1f= -2.49 cm/s and V2f= 5.495cm/s

Go at it....