Atwood's Machine: Quantitative Testing Experiment

Aim

Use Newton's second law to predict how long it will take each object to move 0.5 m after they are released.

Prior Knowledge

• Kinematics: position, velocity and acceleration.
• Newton's second law.
• Pulleys

Description of the Experiment

Observe the experimental setup from the first frame. Consider the forces exerted on each hanging object and use Newton's second law to predict what the acceleration of the orange object will be when the system in released. Then use this value to predict the time. Once you have made your prediction, find the time by analysing the video frame by frame.

Addtional Information

The pulleys used in this experiment have extremely low friction bearings and are very light.

Blue+Green mass:	150g
Orange mass:	200g

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

1. What assumptions did you make about the force exerted by the string on two objects when you drew free-body diagrams? What assumptions about the pulley and the string you need to make to justify this?
2. Did the prediction match the outcome of the experiment? If not, what do you need to revise to make it match?