How Do You Find the Final Speed After a Collision on a Frictionless Ramp?

[physicsperson]

Homework Statement

Well i have a tiny question here

a 2 kg mass starts at rest and slides down a 10 m high, 15 m long frictionless ramp. At the bottom of the ramp it reaches a flat surface where it hits and sticks to a stationary 3 kg mass . Find the final speed of the masses after collision.

Homework Equations

mgh = .5mv^2

The Attempt at a Solution

i was just wondering does the 15 m really matter, where do i use it. I understand the second momentum part of the question but i don't understand what i am supposed to do with the 15 m. All i did was mgh = .5mv^2 and substituted height and mass to get velocity. Please Help.

 

[andrevdh]

Maybe it is not a head on collision in which case the angle is required?

 

[rl.bhat]

When the mass slides down the frictionless ramp, its accelarion is not g but g*sin(theta) where theta is the angle of the ramp to the horizontal. And you can find sin(theta) by using length and height of the ramp.

 

[physicsperson]

thanks

thanks for the help, actually i just omitted the length and used energy equations, and i got the right answer...go figure..