(adsbygoogle = window.adsbygoogle || []).push({}); Two ballbearings are attached to strings of length 3.6m. The mass of ballbearing A is 1.6kg, and B is 1.2kg. Plasticine is attached to each ballbearing, so that they stick together on collision.

The strings are attached to the same place on a roof, so that the ball bearings are hanging next to eachother. Ballbearing A is raised so that its string makes an angle of 50 degrees to the vertical, and then released.

What is the combined velocity of the balls just after they have collided, and what vertical height do they reach?

When the balls are at their maximum height after the collision, their velocity is momentarily zero. Where has the momentum gone?

To find the combined velocity, i just use trigonometry to find the vertical height the balls are raised by (~1.286m). I then used the fact that total mechanical enegery is conserved to find the velocity of A just before it strikes B. Then, using conservation of momentum, i found the combined velocity to be 2.9 m/s.

For the maximum height after the collision, i just used the same idea. I calculated the total mechanical energy just after the collision, using the combined velocity. I then found what height this corresponds to (in terms of gravitational potential energy), since kinetic energy will be zero at the highest point. I got an answer of 0.42m.

Now, both of these answers are correct according to my book, but it doesnt give an answer for the final question, and im not too sure about it. I realise that momentum is conserved, so it cant have just dissappeared. My thought was that it is transferred to the string, but im not very sure about this.

Any help would be appreciated,

Thanks,

Dan.

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# Ball bearings momentum physics problem

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