User:Kruhly/TestLesson/Activities/Guided Activity

Hooke's Law:Guided Activity

Measurements

Activity

The goal of this activity is to determine the spring constant for Spring #1 and learn a bit about Hooke's Law along the way. The activity is broken into two parts. In the first part of the guided activity you will measure the displacement of the bottom of Spring #1 when a mass is attached to it. The second part you will analyze your results. Any time you need help click on the green "Show Help" button. Move the friction slider to the right so it points at "lots". This will cause the mass to come to rest the quickest. Can you think of a reason why? Record your thoughts in your notebook. Make a data table in your notebook with headings called mass, weight, and displacement (see below). Move the reference line so that it is at the bottom of Spring #1. Hang the 50 g mass on Spring #1. Record the mass in your data table. When the mass has come to rest measure the displacement of the bottom of the spring with the ruler. Record the displacement in a data table with headings called mass, weight, and displacement. Make sure to record the units. Repeat steps 2 through 5 with a 100 g mass and then the 250 g mass.

Special thanks to the Physics Education Technology PhET Team <flash>file=MassSpringLab2.swf|width=90%|height=500|bgcolor=#ffffff;|quality=best</flash>

Example data table:

Mass (g)	Weight (N = kg m s−2)	Displacement (cm)

Multichoice Question

What answer best represents the displacement of the bottom of Spring #1 in metres when the 100 g mass is hanging on it and at rest?

(a) 9.8 m

(b) 9.8 × 10−2 m

(c) 4.9 × 10−2 m

Reflection

Reflection

Converting measurements to SI units can be useful when dealing with quantities that have complex units. The best answer to the question above is (b) because the magnitude and units match the theoretical values. If you measured between 9.9 × 10−2 m and 9.7 × 10−2 m you are doing well.

Analysis

Activity

You have completed the first part of the activity and are ready to analyze the data. Proceed with the following instructions: Calculate the Weight in Newtons, N of each mass in your data table. Record the results in the weight column of the data table. Record a sample calculation of the weight in your notebook. Plot a Displacement vs Weight graph. Draw a best fit straight line through your data points. Calculate the slope of the best fit straight line. Record the slope with its units in your notebook. Hooke's Law states that the force on the mass due to the spring is directly proportional to the displacement of the spring. This looks very similar to the slope except that you measured the weight not the force due to the spring. Do you remember the relationship between the weight and the force due to the spring from the first multichoice question? Record the relationship between the weight and the force due to the spring. Determine the spring constant for Spring #1. Record the spring constant in your notebook.