Hooke's Law

Introduction

Hooke's Law explains the elasticity of materials. It states that the force needed to extend or stress a spring is proportional to the elongation or compression. In the language of mathematics, it can be written as

F ~ x

F = -kx

where k is a coefficient that depends on the spring physical properties (stiffness), the spring constant. Minus indicates that an elastic material has an inner ability to return to its regular shape; thus, if an outside force compresses the spring, the "restoring" force acts against it to bring the spring to its shape.

Objectives

The purpose of this experiment is to test Hooke's law for spring and for rubber.

If the spring's elongation is proportional to the applied force, the graph of force vs elongation F(x) should form a line. Does it?
Is the graph for a rubber band similar to the graph created for a spring?

What is Hooke's Law?The spring is a marvel of human engineering and creativity. For one, it comes in so many varieties – the compression spring, the extension spring, the torsion spring, the coil spring, etc. – all of which serve different and specific functions. These functions in turn allow for the creation of many man-made objects, most of which emerged as part of the Scientific Revolution during the late 17th and 18th centuries.

Experiment

Fix a string as shown in Figure 1.
Mark the level of the bottom end of the spring as shown in Figure 2.
Attach a small weight and measure the elongation.
- Remember that the elongation is not the length of the elongate spring!
Collect data in Table 1 of your lab worksheet.
Plot the data in a simple program or on paper (see Figure 4 to arrange the axis)

Repeat all the steps for a rubber band. Compare the graphs.

Figure 1. Spring on a hook

Figure 2. Measuring the length of the spring.

Figure 3. Measuring elongation of the rubber band

Figure 4. Axis for Hooke's Law data

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