## A masses and springs laboratory

In this virtual laboratory you will use an on-line simulation from the University of Colorado PhET group to explore the physics of masses suspended from springs.

Explore the interface!

• You can click and drag a mass to the bottom of a spring and it will hook onto the spring.

• You can click and drag the horizontal (dotted) line to a new position.

• You can click and drag the vertical ruler to a new position.

• In the green control box you can choose operating parameters.

• You can display the components of the energy of one of the mass/spring systems.

• You can turn on a stopwatch.

• You can pause or slow down the motion.

• You can move the mass-spring system to a different location, for example the Moon.

• You can move a slider to change the stiffness of of spring 3.

• You can change the amount of friction in the system.

Experiments

On planet Earth:

• (a)  There is no scale on the slider for friction.  Does the leftmost mark on the slider correspond to zero friction?   Explain how you decided.

• (b)  There is no scale on the slider for the spring constant k (marked softness) for spring 3.  Does the leftmost mark on the slider correspond to k = 0?  Explain how you decided.

• (c)  Move the slider for "softness spring 3" to the middle.  When it is set this way, do all three springs have the same spring constant?  Explain how you decided.

• (d)  What are the spring constants of each of the springs with the slider for "softness spring 3" moved to the middle?

• (e)  There are three unlabeled masses colored red, gold, and green.  What is the mass (in kg) of each of these masses?

• (f)  Display the energy of the #3 system.  Attach the 100g mass to spring 3.  Watch the pattern of the energies change as the mass and spring oscillate.  Describe your observations!  What happens if you change the friction, the softness of the spring, or the mass?  Does the energy display make sense to you?

On Planet X and Jupiter:

• (g)  What is the gravitational acceleration on the surface of Jupiter and on the surface of planet X?
Note: The masses and the spring constants do not change, but the weights do.

Carry out experiments (a) - (g) and answer all the questions (marked up in red).

#### Extra Credit 1 Report:

• In a few words, describe the goal of the experiments.
• Comment on the procedure.  Did you encounter difficulties or surprises?

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