Friction

1. Measure the coefficients of friction.

1. Add a 1,000-g weight to each block and use a scale measure the masses of blocks A and B, including the added mass.
2. Connect the force scale to block A. Pull the scale horizontally and note the reading just before the block begins to slide. Just before it begins to slide, the maximum amount of static friction is resisting the movement. Use the force reading to calculate for block A. Do this five times and record the average value.
3. Repeat step 1.2 with block B.
4. Pull block A across the table at a constant speed. If the speed is constant, then the force reading on the scale should be equal to the frictional force. Calculate for block A. Do this five times and record the average value.
5. Repeat step 1.4 with block B.

2. Effect of weight on the force of friction.

1. Place block A on top of block B and repeat step 1.4 five times, determining the average value. Calculate the factor by which the frictional force increased/decreased.
2. Place block B on top of block A and repeat step 1.4 five times, determining the average value. Calculate the factor by which the frictional force increased/decreased.

3. Effect of surface area on force of friction.

1. Turn block B onto the side that contains only the rim of the pan. The weight will need to be placed on the top of the face-up side. Measure the force of friction and compare it to the value measured in step 1.2. Calculate the factor by which the frictional force increased/decreased.

4. Angle of repose.

1. Place block A on the adjustable incline plane, starting at an angle of 0°. Slowly raise the angle until the block begins to slide. Using a protractor, measure the angle of repose and use Equation 3 to calculate the coefficient of static friction just before the block began to slide. Do this five times and record the average value.
2. Repeat step 4.2 with block B.