I have a couple of physics questions. Any help would be great! A best answer will be chosen.?

Question

1) A 10 kg piece of putty going 3 m/s hits and sticks to a 5 kg puck that is free to slide on the ice. How fast is the puck/putty combindation going immediately after the collision?
3 m/s
6 m/s
2 m/s
45 m/s
2) Answer all that are correct-
You run and jump on a swing. During which of the following motions is the total momentum of you and the swing conserved?
running at the swing (and accelerating)
jumping on the swing (the "collision" between you and the swing)
swinging up on the swing
swinging down on the swing
3)Answer all that are correct-
You run and jump on a swing. During which of the following motions is the total mechanical energy of you, the swing, and the Earth conserved? (Assume that the swing is well made so friction can be ignored.)
running at the swing (and accelerating)
jumping on the swing (the "collision")
swinging up on the swing
swinging down on the swing

Answer 1

Here, For the first Question, the velocity is given by conservation of momentum as (10+5)*v=10*3+5*0.

So, v=2 m/s.(none of ur options.

For the second Question, The momentum is conserved while jumping on the swing. At that point the speed of you and the swing is determined by conservation of linear momentum as well as conservation of Angular Momentum.

During motion, Gravity is acting,which is an external force and hence, Conservation of Momentum is invalid.

For the third Question,Energy can be conserved in this process.

At the time of Jumping on the swing,due to the jerk, an impulsive force acts on the swing due to which Conservation of Energy becomes Invalid.

While Moving up and down the swing, Conservation of Energy can be applied.

Answer 2

1, momentum is conserved so
mv = (m+M)vf where
m = 10 kg, v = 3m/s, M=5kg

so vf = mv/(m+M) = 10*3/(15) = 2 m/s

2. Jumping on the swing. At that point the speed of you and the swing is determined by conservation of linear momentum. The motion of the swing does not conserve momentum because gravity acts on the swing - a force, violating conervation.

3.Same as question 2. The momentum of you+earth and swing + earth is conserved. But only the total momentum is conserved at the moment you adn the swing collide.

Answer 3

Let me see if I have this correct. You are asking a physics question and will pick a "best answer"?
If I get close with my answer, can you just count it correct also, because I tried my best?

Answer 4

m1v1=m2v2
You do the math
The purpose of school is TO LEARN