Starter 1.What is the spring constant for this spring? 2.What is the meaning of the y-intercept? 1.What is the spring constant for this spring? 2.What is the meaning of the y-intercept?

Starter Hooke’s Law If a 1kg mass stretches a spring 2.5cm, what mass would stretch it 10cm?

Hooke’s Law for Springs The force required to stretch a spring is directly proportional to how much it is stretched, or : The force required to stretch a spring is directly proportional to how much it is stretched, or : F = kx F = stretching force in Newtons x= stretch in meters k = the spring constant in N/m

Example When a 10N mass is hung on a spring, it stretches.25m. 1. What is the spring constant? k = F/x = 10/.25 = 40.0 N/m 2. How much would a 20N mass stretch the spring? x = F/k = 20/40 =.50m

Hooke’s Law F =kx If you plot the stretching force on the y axis, and the amount of stretch on the x axis, what will the plot look like? If you plot the stretching force on the y axis, and the amount of stretch on the x axis, what will the plot look like? What does the slope represent? What does the slope represent? Slope = k

Practice - Hooke’s Law m (kg)x(m)F (N) P P

Elastic Forces - Hooke’s Law F = kx k = 10.9 N/m F = kx k = 10.9 N/m

Application - Springs Design an experiment to determine the spring constant for:  1 of the color coded springs  A rubber band Design an experiment to determine the spring constant for:  1 of the color coded springs  A rubber band Make a F vs. x graph for each with 5 data points. Show a best fit line and determine the equation and k. A A

Procedure 1.Put the force sensor on the stand. 2.Put the spring on the sensor. 3.Put a weight hanger on the spring with enough mass to open the spring up. 4.ZERO THE FORCE SENSOR. 5.The bottom of the hanger is now at the starting position. 6. Add some weight and see how much the spring stretches from the starting position. 7. Record the weight and the stretch. 8. Repeat with more weight. Remember you are always measuring the stretch from the original starting position. 9.After 5 data points, plot F vs. x and get the slope. That is your k value. 10. Repeat for the rubber band. Open “ Hooke’s Law” loggerpro file on the K drive.

Question Did the rubber band obey Hooke’s Law? Explain with reference to your graph. Did the rubber band obey Hooke’s Law? Explain with reference to your graph.

Lab Report Checklist 1.Starter 2.Data Tables (2) 3.Sketch F vs. x Graphs (2) with slopes 4.Experimental k value for spring (1) 5.Question 6.Connection 7.Summary 1.Starter 2.Data Tables (2) 3.Sketch F vs. x Graphs (2) with slopes 4.Experimental k value for spring (1) 5.Question 6.Connection 7.Summary

Connection What real life applications of Hooke’s Law have you observed? What real life applications of Hooke’s Law have you observed? C C

EXIT Summarize your experiment including the objective, the procedure, the results, and reasons for error. Summarize your experiment including the objective, the procedure, the results, and reasons for error. E E