Thread: Momentum Problem

Bullet of mass 0.05 kg is fired from a gun with velocity 700 m/s, find the momentum of the gun immediately after it's fired?

I used Momentum = mv = ? - Here I'm taking the direction of the bullet as positive.

If the gun is brought to rest in 1s by a horizontal force that rises uniformly from 0 to Z N, then falls uniformly back to 0 again, find the value of Z.

No idea how to start this really. Was thinking to try and find the average acceleration and then use , however the acceleration isn't constant, so this wouldn't work would it?

Would love it if someone could give me a little pointer on this?

Thanks in advance

Let represent the force on the gun. Then the impulse is equal to the change in momentum:



Since the force increases and decreases uniformly,



And f(t) is the equation of a line from 0 to 0.5: f(t) = kt + c

But c = 0 since f(0) = 0,

so solve for k.

Then .

Again sorry for the late reply.

Thanks a lot for your reply, would have never thought to do it this way.

Solving the integral above you get , .

Putting this back into the equation of the line, we get the value of Z to be 70?

Thanks again for the help

Yes, the value of Z is 70.

Thanks again, your a life saver!