- #1

Juntao

- 45

- 0

a) velocity of car 1 =?

b) velocity of car 2 =?

I know that for this problem, I got to use conservation of momentum and conservation of energy, but I don't even know how to even start off this problem. Major help needed!

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- Thread starter Juntao
- Start date

- #1

Juntao

- 45

- 0

a) velocity of car 1 =?

b) velocity of car 2 =?

I know that for this problem, I got to use conservation of momentum and conservation of energy, but I don't even know how to even start off this problem. Major help needed!

- #2

NateTG

Science Advisor

Homework Helper

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You need to apply two equations:

1. Conservation of energy.

2. Conservation of momentum.

1. Conservation of energy.

2. Conservation of momentum.

- #3

Doc Al

Mentor

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What's the initial momentum of the system? (Hint: the masses start from rest.) What's the final momentum (m

What's the initial KE of the masses? (see previous hint).

How much energy is stored in the compressed spring?

What's the final KE of the masses?

- #4

Juntao

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Baby steps, right?

Ok. Initial momentum equals final momentum.

and I realized objects start from rest, so initial velocity is zero

thus,

initial momentum =0

so 0=(m1v1+m2v2)

or -m1v1=m2v2

Ok, that part wasnt so bad.

Initial KE=0

Final KE= .5m1v1^2+.5m2v2^2

Spring potential energy=.5kx^2

ah, so yea, I guess then .5m1v1^2+.5m2v2^2=.5kx^2

Ok. Initial momentum equals final momentum.

and I realized objects start from rest, so initial velocity is zero

thus,

initial momentum =0

so 0=(m1v1+m2v2)

or -m1v1=m2v2

Ok, that part wasnt so bad.

Initial KE=0

Final KE= .5m1v1^2+.5m2v2^2

Spring potential energy=.5kx^2

ah, so yea, I guess then .5m1v1^2+.5m2v2^2=.5kx^2

Last edited:

- #5

Doc Al

Mentor

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Yep. You're half-way home.Originally posted by Juntao

So for the energy part, is it going to be like the KE of both carts equal the potential energy of the spring?

so like this:

.5*m1v1^2+.5m2v2^2=.5kx^2

- #6

Juntao

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- #7

Doc Al

Mentor

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Sweet.

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