# Workout: Hanging mass on a spring

the pages mass on a spring and hanging mass on a spring

## Launch

To give you some experience with oscillations, go to the PhET simulation, Mass-spring lab to perform a few tasks.

## Set up

Launch the simulation and hang a 100 g mass from spring 3. Wait until the oscillation dies down. Your screen should look like the figure at the right.

1. There is no scale on the "softness of the spring" slider. With the slider set at the default value (middle mark) find the spring constant for spring 3. (Use g = 10 N/m and give your answer to 2 sig figs.)

2. By changing the slider to a different softness, figure out how much of a change in k changing the slider by 1 mark makes.

3. Now set the friction to 0, the softness of spring 3 to the middle value, and click the button to "Show Energy of 3". (Depending on the speed of your computer, you might find it useful to also click the button "1/16" time.) Pull the 100 gram weight down 30 cm. Describe the division of energies at this instant of time.

4. Now release the mass and watch it oscillate. Describe what happens to the energies as it moves through the cycle, being careful to "open up" the story so you can see how energy is being exchanged as it rises and falls.

5. Does the spring PE ever go to 0? Explain why or why not.

Joe Redish, Spring 2017

Article 674