conservation of momentum

[TonyHem]

3) A 200g snooker ball travelling with initial velocity to the right collides with a stationary ball of mass 100g.If the final velocity of the 200g ball is to the right, calculate the velocity of the 100g ball after the collision.

[Flaming_Arrow]

right

[TonyHem]

omg Lol, i had that 2nd last line o_0. For some weird reason I kept trying to divide the 1.8 with the 0.6.

[Edmund]

Well I typed this up already maybe you want to look at it =P

M.U + m.u = M.V + m.v

where

M is the mass of 200 gram snooker ball
U is the initial velocity of the 200 gram snooker ball [9.0ms^-1 to the right]
m is the mass of the 100 gram snooker ball
u is the initial velocity of the 100 gram ball [stationary, so 0ms^-1]
V is the final velocity of the 200 gram snooker ball [3.0ms^-1 to the right]
v is the final velocity of the 100 gram snooker ball [we find this]e for v.

Sub in all values and solve for v.

[TonyHem]

Just a quick question:
It says a railway water tanker loses a certain amount of water. 1 Person says that because its lost mass, the tanker will speed up. The other says the speed of the cart wont change and the momentum will be conserved.

My question is: If you were being held back by a huge bag of books, and then say the bag tears open and the books drop out, wouldnt you be able to travel faster? Or do you like speed-up because you've lost the books , so that when you times the new mass and velocity, it still has the same momentum as it did originally?

[Edmund]

p = m.v

If mass decreases, velocity increases, given momentum is constant.

[Mao]

This one is debatable. I think It will keep travelling at the same velocity [assuming the engine is only supplying enough power to counter the frictional forces]. Water being released does a velocity [same as the tanker] and does have momentum, thus by the conservation of momentum, the tanker does not move any faster. However, it is able to accelerate faster since the mass is smaller [hence the same amount of force would cause higher acceleration].