Homework Help: Physics

Posted by Alex on Sunday, May 18, 2008 at 4:28pm.

A 3.0kg air puck sliding at 4.0m/s collides with a 5.0kg puck. After the collision the 3.0kg puck is moving north at 1.0m/s while the 5.0kg puck is moving south at 1.0m/s.
a) What was the initial velocity of the 5kg puck?

I did:
m1v1 + m2v2 = m1v1' + m2v2'
(3)(4) + (5v2) = (3)(1) + (5)(1)
and got -0.8m/s for v2.

b) What percentage of the initial kinetic energy remained after the collision?
I did
KE1' + KE2'
----------
KE1 + KE2
and got 16%

Now these questions I'm completely lost with because of the angles.

2) A 3kg ball moving east strikes a 2kg ball that is moving east at 2m/s. Following the collision the 3kg ball moves at 4m/s in a direction [E55S] while the other ball moves in a direction of [E35N].

a) By considering components of momentum in a N-S direction, calculate the speed that the 2kg ball had after the collision.
b) By considering conservation of momentum in an east-west direction, find the initial speed of the 3kg ball.

3) A 20kg child sitting on smooth ice is sliding straight north at 2m/s when she throws a big 2kg snow ball which (after the throw) moves [N60E] at 10m/s.
a) Calculate the momentum, speed and direction of motion of the child following the throw.

Physics - Damon, Sunday, May 18, 2008 at 4:54pm
2) A 3kg ball moving east strikes a 2kg ball that is moving east at 2m/s. Following the collision the 3kg ball moves at 4m/s in a direction [E55S] while the other ball moves in a direction of [E35N].

a) By considering components of momentum in a N-S direction, calculate the speed that the 2kg ball had after the collision.
-------------
a)
Initial momentum N is zero
final momentum N:
0 = 2 (s sin 35) - 3 (4 sin 55)
s = 12 sin 55 / 2 sin 35 = 9.83/1.15
s = 8.55 m/s
=========================

b) By considering conservation of momentum in an east-west direction, find the initial speed of the 3kg ball.
--------------------------------
initial momentum E = 3 v + 2*2 = 4 + 3 v
final momentum E = 2*8.55 cos35 + 3*4 cos 55
so
4+3v = 14+6.88
3 v = 16.88
v = 5.63
Physics - Maddie, Monday, April 22, 2013 at 9:40am
What about the answer to #3?

Answer this Question

Related Questions

Physics - Two identical pucks are on an air table. Puck A has an initial ...
phtsical science - Which has greater momentum, a 2.0kg hockey puck moving east ...
physics help please - an air puck of mass m1= 0.25 kg is tied to a string and ...
Physics - Two pucks collide on a level air-hockey table. Puck A has a mass of 0....
Physics - The drawing shows a collision between two pucks on an air-hockey table...
Physics - An air-hockey puck of mass m floats across the table essentially ...
physics - An ice hockey puck slides along the ice at 12m/s. A hockey stick ...
physics - A collision occurs between two pucks on an air-hockey table. Puck A ...
physics - A 3.0 kg sphere moving to the right at 2.0m/s undergoes an elastic ...
Physics - An elastic collision occurs between two pucks on an air-hockey table. ...

For Further Reading

First Name:
School Subject:
Answer: