What Is the Speed of Particle Q After the Collision?

[nasadall]

Homework Statement

Two particles P and Q of mass 2kg and 5kg respectively are moving towards each other along a straight line on a smooth horizontal surface. The particles collide. Before the collision the speeds of P and Q are 6m/s and 4m/s respectively. After the collision the direction of motion of P is reversed and its speed is 1.5m/s. Find:

i) The speed and direction of Q after the collision.

Homework Equations

m1 u1 + m2 u2 = m1 v1 + m2 v2

v2 = (m1 u1 + m2 u2 – m1 v1) / m2

The Attempt at a Solution

v2 = (2 6 + 5 4 – 2 1.5) / 5

v2 = (12 + 20 – 3) / 5

v2 = 29 / 5

v2 = 5.8m/s-1

I think this equation is right and that the directiond of q would maintain if p is reversed.

ii) The magnitude of the impulse given by P to Q in the collision

i think this is the equation:

I = m_p(v-u)

can someone confirm??

please

 

[kuruman]

If the particles are initially moving in opposite directions, their initial velocities must have opposite signs. Do they?

 

[nasadall]

you are right, say Q in possitive and P negative!

 

[kuruman]

you are right, say Q in possitive and P negative!

And how would that change your momentum conservation equation?