Determining the Coefficient of Friction, µ (mu)
Obj: Determine µ for an object on a 3 different surfaces.
Materials: objects, 3 study surfaces, balance, Newton scale
1. Sketch the setup showing the free-body diagram of the object being pulled at constant velocity by the Newton scale on the study surface.
2. Determine the weight of the object. On a horizontal surface, weight equals FN.
3. Hook the scale to the object, then using a horizontal force, pull on the scale with a gradual increase in force until it starts moving along the study surface at constant velocity. Record the approximate force on the scale to start the object and the force to maintain its constant velocity.
4. Calculate the μs and μk values for these two surfaces using the equation for frictional forces.
5. Repeat for one other surface, then surmise the possible cause of frictional force differences.
6. Add to your object a 500g or 1000g mass, then determine μs and μk for one surface and compare.
7. What applied force would be required to accelerate the blocks at 1.5 m/s2? What μ value did you use in this calculation of net force?
8. How is total friction reduced in (a) automobile engines (b) hovercraft.
9. How do antilock brakes (ABS) increase the braking force while stopping? What μ value does this represent?
10. How does increasing the angle of the incline affect the FN, μ, and the Ff?
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