Any ideas?

Any ideas?
Im not even entirely dure of what I am being asked.

go ask in math and science OP

Good point

Not for homework help. Also /sci/ is way stupider than Sup Forums.

it says:
a) Show that the speed of Q after the collision is (u/7)*(15e+1).
b) Given that the direction of motion of P is unchanged, find the range of possible values of e.

I know. But how do i show that

probably by relating conservation of momentum with the coefficient of restitution. My physics is rusty so i cant come up with a direct solution, but i think thats how you're supposed to go about it

Look up equations for elastic collisions, I think that is what is needed here

I can do it with numbers but i lose nyself with the letters. It gets really complicated.

aaah, yeah thats why they assign these. you have to learn to relate the variables to what they mean. When you find their meaning, you can substitute the right stuff in order to end up with what they want you to show. Sorry im not of better help, i finished all the physics i needed and deleted it off my brain haha.

I lose myself in the music, the moment, i own it, I'll never let it go

m1*v1=m2*v2, just apply conservation of momentum. gg

i think the part that is tripping op up is the constant of restitution and how to end up with the final answer that they want him to reach.

Yes

coefficient of restitution e = (speed a after - speed b after)/(speed a before - speed b before)

typically 0

fuck messed up, (a-b)/(b-a)

How do i apply that to the question

1 sec, it's just a simple simultaneous eqn, doing it now.

Ok

I'm pretty sure my logic is correct, but I don't seem to be getting the correct answer.

Closer than i can get

The process for all these questions is to use the conservation of momentum to get an equation in terms of P' and Q' (final velocities) and rearrange the constant of restitution to get another equation in terms of P' and Q' and solve simultaneously.

Could you show me. I get lost with the letters. It gets complicated quickly

okay worked it out. I got the direction of the initial speed in the coefficient of restitution equation wrong. it should be e = (P'-Q')/(-2u-3u)
That gets the correct answer of

P' =-u(20e-1)/7
Q'=u(15e+1)/7

Legend

Equation 1: Conservation of linear momentum
Momentum initially = Momentum final.
(remember that these are vectors)
(Momentum is mass * velocity)
Assuming positive to the right, P weights 3m units, and is going 3u m/s to the right

Therefore its momentum is 3m*3u (positive)

Q weighs 4m units, and is going 2u m/s to the left

Therefore its momentum is 4m*2u (negative)

Initial momentum = 9mu - 8mu

Do the same for the final momentum, but as we don't know the final speeds leave as P' and Q'.

Thus: 9mu - 8mu = 3m*P' + 4m*Q'

Equation 2: Coefficient of restitution

e = (P' -Q')/(Q-P)

We know that Q = (-2u), P = 3u

Now you have 2 equtions and 2 unknowns solve for P' and Q'

Does that all make sense?

I'm not quite sure about part B, I think I am over complicating it. But if P' =-u(20e-1)/7 and Q'=u(15e+1)/7. It implies that The balls collide and bounce away.

To keep P going in the same direction, -u(20e-1)/7 > 0

-u(20e-1)>0
(20e-1)>0
20e>1
e>1/20

But we know that 0

Yes i follow