Pendulum Projectiles…HOW DO WE DO THIS?!

Please study the below diagram:

Feel free to brainstorm for the following questions in consideration of the lab activity tomorrow.

- You pull the pendulum back. How might you be able to determine the amount of GPE you are giving the pendulum?
- You let go of the pendulum and it swings through its rest position. How could you calculate how fast it is going?
- The pendulum string is cut! Now the pendulum has entered into horizontal projectile motion! How might you find where it will hit the ground? (aka the Range!)

Now, several things you will have needed to consider include:

- GPE
- KE
- Conservation of Energy
- Projectile Motion
- Initial Velocity, Final Velocity
- Horizontal and Vertical Components (think back to first semester!)
- Acceleration Equations (Equation sheet???)

Using everything we have talked about over the course of the last 5 months, work through the problem below:

You pull back a 50-g pendulum bob so that it has been raised a height of 4.5 cm from its rest position. The pendulum is sitting 50 cm off the floor.

A. Find the change in GPE (added energy)

B. Now, you let it go. Find it maximum velocity at the rest position just before the string is cut!

C. Now, using a toolkit, find where the projectile will hit the floor!

You are going to perform this procedure in the lab tomorrow. You will get one chance to achieve 100%. If you have questions about certain aspects of the problem please contact me. However, you will need to provide me with your answers to questions #1-3 above so that I know you have given consideration to the problem. Best wishes! I am confident you, like the many physics students before you, will do quite well!

What equation should we use/modify to find the distance?

There is no particular equation. You need to create a toolkit and look at the horizontal and vertical components of motion. You need to find what it is you’re looking for and use your equation sheet to assist you. I think you will probably need 2-3 equations when it is all said and done.

Does the “4.5 cm” refer to vertical displacement, or is it the total distance the bob is moved diagonally?

Vertical displacement! Great question!