Double Pulley Pendulum: Application Experiment

Aim

This is a good application of Newton's laws, kinematics and circular motion.

Prior Knowledge

• Newton's Laws (all three).
• Circular motion.
• Free-body diagrams.
• Vectors.

Description of the Experiment

Two objects of equal masses, connected by a string, are suspended over a pair of low friction pulleys. One of the objects is pulled back and made to swing like a pendulum. Use your knowledge of kinematics, Newton's laws and circular motion to make a precise prediction about the motion of the second object after the first begins to swing.

Addtional Information

Hint: This is a difficult problem to calculate. If you are stuck, use the previous experiment as an observation experiment to help you make a good prediction for this experiment. Count the number of frames when the tension in the string is more than the weight of the bob and the number of frames then the tension is less than the weight of the bob.

Youtube movies can be stepped frame by frame using the , and . keys on your keyboard. If you want to download the movie to your computer, right-click or control-click HERE.

Questions

Now that you have watched the video, did your prediction agree with the outcome of the experiment? If your prediction did not match the outcome, try and use your physics knowledge to explain what you see.