You are here:
Labs › exp Work & Energy › WE Exp Spring

In this part you will measure the work needed to stretch a spring. Unlike the work needed to lift a mass, the work done in stretching a spring is not a constant. The work can still be calculated using the area under the force *vs.* distance graph.

**1**. With the "*WorkEnergy*" experiment loaded, change the force scale of the Force/Time and Force/Distance graphs to go from 0 to 0.6N.

**2**. Attach one end of the spring to a rigid support and the Force Sensor hook to the other end. Rest the Force Sensor on the table with the spring extended but relaxed, so that the spring applies no force to the Force Sensor. Place the Motion Detector about one meter from the Force Sensor, along the line of the spring. Be sure there are no nearby objects to interfere with the distance measurement.

**3**. Using tape, mark the position of the leading edge of the Force Sensor on the table. The starting point is when the spring is in a relaxed state. Hold the end of the Force Sensor that is nearest the Motion Detector as shown in Figure 3. The Motion Detector will measure the distance to your hand, not the Force Sensor.

**4**. Click "*Start*" to begin data collection. Within the limits of the spring, move the Force Sensor and slowly stretch the spring about 50 cm over several seconds. Hold the sensor still until data collection stops. Do not get any closer than 40 cm to the Motion Detector.

Try this a few times till you feel you have a set of data representative of your experiment.

**5**. Sketch the three graphs into your notebook

**6**. Examine the distance *vs.* time and force *vs.* time graphs by clicking the Examine button . Identify the time when you started to pull on the spring. Record this starting time and distance in a data table and on your sketched graph

**7**. Examine the distance *vs.* time and force *vs.* time graphs and identify the time when you stopped pulling on the spring. Record this stopping time and distance in a data table and on your sketched graph

**8**. Click the force *vs.* distance graph, then click the Linear Regression button to determine the slope of the force *vs.* distance graph. The slope is the spring constant, k. Record the slope and intercept.

**9**. The area under the force *vs.* distance graph is the work done to stretch the spring. How does the work depend on the amount of stretch? On the force *vs.* distance graph select the region corresponding to the first 10 cm stretch of the spring. (Click and hold the mouse button at the starting distance, then drag the mouse to 10 cm and release the button.) Click the Integrate button to determine the area under the force *vs.* distance curve during the stretch and record this area in your data.

**10**. Now select the portion of the graph corresponding to the first 20 cm of stretch (twice the stretch). Find the work done to stretch the spring 20 cm and record this in your data.

**11**. Select the portion of the graph corresponding to the maximum stretch you achieved. Find the work done to stretch the spring this far and record in your data.