Pendulum Problem: AP Physics 1985B1

[hty21]

A 2-kilogram block initially hangs at rest at the end of two 1-meter strings of negligible mass as shown on the diagram above (I'll explain this later). A 0.003-kilogram bullet, moving horizontally with a speed of 1000 meters per second, strikes the block and becomese embedded in it. After the collision, the bullet/ block combination swings upward, but does not rotate.
The diagram shows pretty much everything described above. It doesn't give how far apart the strings are from each other/ the block, etc.
a. Calculate the speed v of the bullet/ block combination just after the collision.
b. Calculate the ration of the initial kinetic energy of the bullet to the kinetic energy of the bullet/ block combination immediately after the collision.
c. Calculate the maximum vertical height above the initial rest position reached by the bullet/ block combination.

m1v1 +m2v2 = m1v1' + m2v2'
KE= 0.5 m v^2

I got all the answers using the kinetic/potential energy equations above, and assuming that only one string was holding up the block (like a pendulum). I could write out the work I did to get these answers if you would like. But my main question is: how does having two strings attached to the block affect my answers? I think that, if you attach more strings, and attach the strings closer to the ends of the block, the block will move less. But the problem doesn't give any string measurements in relation to the block - only that the string itself is 1m long.

I would appreciate any ideas or insight. Thanks in advance!

p.s. How do you use the template when starting a topic? thanks!

 

[LowlyPion]

I can't see your diagram, but I suspect the idea of the 2 strings is that it will prevent lateral rotation, i.e. that they are side by side and the bullet strikes between more or less in line with the block's center of mass.

In which case the ballistic pendulum reduces merely to solution along the lines you have outlined. Momentum is conserved and then the Kinetic Energy will become potential and hence height can be determined.

As to using the template you should enter text between the headings that are automatically supplied.

 

[thomate1]

I would like to commend you for your efforts in solving this pendulum problem and seeking further understanding of the concept. I will address your main question first and then provide some general guidance on using the template when starting a topic.

To answer your question, having two strings attached to the block will affect the movement of the block after the collision. This is because the two strings will exert different forces on the block, resulting in a different trajectory compared to if only one string was attached. The exact effect will depend on the placement and tension of the strings, as well as the mass and velocity of the bullet.

In order to accurately solve the problem, you would need to know the exact placement and tension of the strings in relation to the block. Without this information, it is difficult to say how the answers would be affected. However, it is safe to assume that the block will have a slightly different trajectory and potentially reach a different maximum height than if only one string was attached.

As for using the template when starting a topic, it is recommended to include a clear and concise title that summarizes the main topic or question. In your case, a suitable title could be "Effects of Multiple Strings on a Pendulum Problem." Then, in the body of the post, you can provide a brief introduction to the problem and your current understanding, followed by your main question or concern. This will help others better understand and respond to your topic. Additionally, you can use bullet points or numbered lists to organize your thoughts and make it easier for others to follow your reasoning.

I hope this helps. Keep up the good work in solving challenging problems and seeking further understanding!