Starter

1. Starter A bar is pivoted as shown. To make the bar spin, a force is applied. This makes the bar have an angular acceleration. How would you adjust F, r and q to get a large angular acceleration? Make r = length of the bar, put F at the end with q =90o.

2. Torque, t • The turning rate depends on : • Where you put the force • What direction the force acts • How much force you use • t = rFsinq • ( units = N.m )

3. Torque, t • If you push perpendicular to the object, then: • t = rF • ( units = N.m ) If this wrench is 50cm long and you push with 100N of force, what is the torque on the pipe? t = rF = .50(100) = 50.0 N.m

4. Torque Experiment – Put in Science Notebook Put the stick on the stand and adjust the pivot until the stick balances all by itself. Hang m1 and m2 (m1≠ m2 ) by string loops or hangers and move them until the system balances. Measure and record m1, m2, r1 and r2. ( Use kilograms and meters.) Calculate the ccw torque, the cw torque, and the percent difference. Repeat for a total of 5 trials. Do 3 more trials that each use of 3 masses – 2 on one side, one on the other.

5. Data Table for Notebook

6. Questions in Science Notebook What would have happened if the stick had not been balanced at the start? 2. Place the pivot on the stick at the 25cm mark. Balance the stick with a mass at the 0 mark. ( You may have to tape the loop to make it stay right at the end of the stick.) Compare the mass of the stick to the mass you used to balance it. How do they compare? Why?

7. Science Notebook Report Checklist Starter Data table Sample Calculations Questions (2) Summary