A 35.0-g bullet strikes a 4.7-kg stationary piece of lumber and embeds itself in the wood. The piece of lumber and bullet fly off together at 8.0 m/s. What was the original speed of the bullet?
I don't know where to begin...

This one too pleeasee

A thread holds a 1.5-kg and a 4.50-kg cart together. After the thread is burned, a compressed spring pushes the carts apart, giving the 1.5 kg cart a speed of 27 cm/s to the left. What is the velocity of the 4.5-kg cart?

I would be so grateful if someone could help me..

rl.bhat
Homework Helper
Just go through the conservation of linear momentum.

Hi there. Is conservation of linear momentum something you have studied in class?

Also: I would start a new thread for each problem, else things get confusing/messy.

Yes, im in the ib program but i was absent for that lesson..
ha thanks for the heads up, i just started this
Andd thank you both for the help

Yes, im in the ib program but i was absent for that lesson..
ha thanks for the heads up, i just started this
Andd thank you both for the help

Okay, well paraphrasing Conservation of momentum says that if no external forces act on a system (which is true in this case), then the total linear momentum is conserved.

That is, $\sum mv_{initial}=\sum mv_{final}$

In this case,

$$M_{bullet}V_{bullet}+M_{block}V_{block}=M_{(block+bullet)}V'_{(block+bullet)}$$

where I used the ' symbol to indicate velocity after the collision

And Yes, they are both conservation of momentum.

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