# Newton's Second Law

In this lab, you will determine the coefficient of static friction between a wood block and the masonite laboratory bench top using the technique you designed in the prelab.

## Procedure

• It is important that the string be parallel to the table.
• Make at least 10 trials.
• Notice that the mass of the hanger is 5 grams.
• For the error in the hanging mass m2, use the standard deviation of the mean (SDOM). See Taylor section 4.4 if you are confused.
• Turn the block on a side with different surface area in contact with the bench and repeat the measurements.
• Return the block to its original orientation, add a 200-gram mass to the top of the block, and repeat the measurements.

## Error analysis

• What is your calculated value for s in each of the three cases (flat, side, weight on top)?
• Include an error estimate for s in each case.
• What are the units of s?
• Why is it important that the string be parallel to the table?
• Does s change appreciably when the contact area is changed?
• Does s change appreciably when mass is added to the block?
• Do the three determinations of s agree? That is, do their errors overlap? See Taylor page 5 if you are confused.
• Identify at least two sources of statistical error.
• Identify at least two sources of systematic error.

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