Work out the velocity from the momentum?

[ryansmith885]

Homework Statement

Does anyone know if it is possible to work out the velocity from the momentum?
206Kg ms^-1 is the momentum... thanks
ryan

Homework Equations

The Attempt at a Solution

 

[learningphysics]

do you have the mass?

 

[ryansmith885]

no i don't have the mass just the mometum

 

[learningphysics]

no i don't have the mass just the mometum

Then it's impossible to get the velocity... the velocity could be anything...

momentum = mv
v = momentum/m

plug in difference m's and you get different v's...

 

[ryansmith885]

thanks for the formula... if two skaters collide 1 has 75kg mass (180kg ms^-1 momentum) and the other has 60kg mass (100 kg ms^-1 momentum) than the total size of momentum before the collision would be 206 kg ms^-1 right? I want to calculate the velocity of 206kg ms^-1 thanks

 

[ryansmith885]

i made these mass's up

 

[learningphysics]

thanks for the formula... if two skaters collide 1 has 75kg mass (180kg ms^-1 momentum) and the other has 60kg mass (100 kg ms^-1 momentum) than the total size of momentum before the collision would be 206 kg ms^-1 right? I want to calculate the velocity of 206kg ms^-1 thanks

How do you get 206?

you need to consider direction also... if they collide I assume they're going in opposite directions?

Then if the momentum of the first is 180, and the other is 100 in the opposite direction... I'll call it -100 taking the direction of the 1st skater as positive...

so total momentum = 180 + (-100) = 80kg*m/s

So total momentum after the collision is also 80kgm/s by conservation of momentum.

Now once they collide are they sticking together? Then using the definition of momentum and a total mass of 75kg+60kg... you can solve for the velocity using the momentum of 80kgm/s.