PreLab: springs
The PhET group has created an online
simulation that parallels aspects of the lab
that we will be doing. The simulation can be
accessed online at:
http://phet.colorado.edu/sims/mass-springlab/mass-spring-lab_en.html. The springs in
the simulation are IDEAL SPRINGS. This
means that they have characteristics that
follow the relationship known as Hooke’s Law.
The equation that describes this relationship
is given in section 10.1 of your text.
Look up this equation. Write it and state where it was found using a citation.
State the meaning of each variable in the equation.
Step 1: Run the simulation to make sure that you understand how to move the items and make
measurements.
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
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Click and drag a mass up to the bottom of one of the springs. It will hook and stay on the spring,
causing it to stretch.
Click and drag the horizontal, dotted line up and down. It will be used later to assist with
making measurements.
Click and drag the ruler to a new location. This is the ruler that you will use later to make
measurements of the position of the bottom of the spring.
You can pause or slow down the spring oscillations using the buttons in the time box. There is
also a stopwatch available. We will not be using the simulation while the mass is moving so
neither the time box nor the watch will be necessary for this exercise.
Notice the spring softness adjustment. These marks will be referred to by a number between 0
(soft) and 10 (hard).
Step 2: Initialize the settings.
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Set the friction slider to lots.
Move the horizontal dotted line to the bottom of the unstretched springs.
Place the ruler so that 10 cm is the position of the horizontal dotted line.
Step 3: Simulation.
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Place the 50 g mass on spring 1 and record its mass and the position of the bottom of the spring.
Repeat with the remaining silver masses.
Results
Mass
(
)
Complete the table below and graph Weight vs
Extension. (Uncertainty is not necessary in a
simulation.)
Sample Calculation for spring Extension

Spring
Extension
(
)
0
Sample Calculation for Weight of Mass
Graph of Spring Extension vs. Weight of Mass
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Position of
bottom of
spring (
)
Label your graph axes
Draw the best fit line
Place the Yellow mass on spring 1. Use
your graph to find its weight. Show
your method on the graph.
Write the equation of the best fit line.

Is this equation the same as Hooke’s
Law? What is k?

Use your equation to find the weight of
the yellow mass. Show your work.

What is the mass of the yellow object? Show your work.
Weight
of Mass
( )
Apply your understanding:
1.
In what way (if any) would your graph change if you had set the ruler so that its zero value was
at the top of the spring? Give a reason.
2. In what way (if any) would your graph change if you used spring 2? Give a reason.
3. In what way (if any) would your graph change if you used spring 3 with the softness setting on
the 6th mark from the left (the middle is considered the 5th mark)).
4. In what way (if any) would your graph change if you set the simulation as if you were on the
moon?