- #1

NoHeart

- 28

- 0

easiest one first:

1. A 3kg ball of putty moving at 1m/s collides and sticks to a 2kg ball at rest. The putty and the ball then move with a momentum of what?

so far i have initial momentum of putty at 3Ns (3kg*1m/s) and then I'm not quite sure... initial momentum of other ball is zero? (2kg*0m/s=0Ns)

so do they both keep moving with a momentum of 3Ns? or is the force not enough for them to move, and it's 0Ns? I'm thinking the momentum cannot remain constant because the mass has changed...so would it be correct to say 3kg-2kg=1kg, and that momentum would equal 1Ns? I'm thinking this is the answer (1Ns) but I'm not sure if I'm grasping the concept correctly...

2. a 20g bullet travels at 350m/s, strikes metal plate at an angle of 30, bullet ricochets off at same angle with a speed of 320m/s- What is the magnitude of the Impulse the wall gives to the bullet?

this is giving me a lot of trouble, I'm not sure what to do with the angles...the diagram shown has the bullet traveling at an angle pointing up towards the wall, and ricocheting off upwards, so the angles are in reference to the y-axis...

if impulse is a change in momentum, i have initial momentum at 7Ns (20g*350m/s) and final momentum at 6.4Ns, so the impulse would be

6.4-7= -0.6Ns

that's not anything close to what i think the answer is, i know i should be using sin or cos30 at some point, but where? and is the initial momentum going to be negative because it is coming from the negative x-axis?

i am so confused...

3. a 10.5g bullet strikes a 3kg wood pendulum and imbeds in the wood. the pendulum rises by 0.22m after impact, What was the initial velocity of the bullet?

okay, so lost. the initial momentum has to equal the final momentum, right? but how do i find momentum without velocity? i could find the final momentum using the distance of 0.22m, but i don't know the time. where do i even start here?