Swing the Stopper Lab

The goal of this lab is to use a rotating stopper to find the mass of various objects that you can hang from a paper clip. These objects should be found around your house.

The basic set up is to attach an object and swing the stopper in a horizontal circle above your head. The data that you will be collecting will be the time it takes to complete 20 revolutions of the stopper. Be sure that the stopper rotates horizontally and that the motion is constant so that the hanging object does not move up or down as the stopper is swinging. You will also need to know the radius that the stopper is rotating. To collect this, you will need to grab the end of the string by the handle (center of rotation) after you have the 20 rotations. Use a ruler to measure the length in meters.

After the data is collected, you will calculate the mass of the hanging object by using the FBDs for both the object and the stopper. The stopper's mass is recorded on the bag that it came in.

This process will be repeated for 3 different objects.

After this is completed, answer the questions at the end of the lab.

The Data - Insert a picture of the three objects above the table.

Object	Time for 20 Revolutions (s)	Radius (m)	Stopper Mass (kg)
scissors	9.39	.64	0.02536
weight	8.29	.34	0.02536
eraser	7.20	.30	0.02536

Calculations - Post a picture of your work for one object below the second table.

Object	Angular Velocity (rad/s)	Tangential Velocity (m/s)	Centripetal Acceleration (m/s2)
Scissors - 82g
Eraser - 13g
Weight - 500g

Object	Centripetal Force (N)	Weight of Object (N)	Mass of Object (kg)
Scissors
Eraser
Weight

The Questions - all answers in the boxes.

What direction would the stopper fly if the string was to break as you were swinging it with a constant velocity?

What do you have to do in order to make the hanging mass move up? Move down?

If you maintain a constant rotational speed and pull the hanging mass down. What is the relationship of the rotational speed to the radius under this constant force?