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Investigate friction and measure the coefficients of friction.

Friction is the force that opposes the motion of two surfaces that are in contact. The direction of the force is parallel to surface and is equal to and opposite of the force producing the sliding (Newton's third law). The properties of the surfaces in contact μ (mu) and the normal force Fn pushing the surfaces together determine the frictional force Ff generated.

Wood block; 500 g hook mass, 1000 g hook mass, spring scale (with capacity large enough to measure the weight)

Friction Equation

Part A - Wood Block
1. Use a spring scale to find the weight (N) of the wood block and record.
2. Slowly, pull the block along the tabletop at a constant speed using the spring scale. Observe and record the frictional force (N).
3. Calculate the coefficient of friction between the table top and the wood block.
4. Repeat two more times and calculate the average coefficient of friction for the three trials.

Part B - 500 g Metal Hook mass
1. Repeat the experiment above using the 500 g hook mass.

Part C - 1000 g Metal Hook mass
1. Repeat the experiment above using the 1000 g hook mass.

1. Does increasing the weight of the object increase the coefficient of friction? Explain.

2. Which has a higher coefficient of friction against the tabletop, wood or metal?

1. If the coefficient of friction of ice against rubber is 0.05, how much frictional force would a 560 N bicycle and rider have against an icy sidewalk?

2. How would adding a lubricant such as oil have changed the results of your experiment?