# Predict the motion of a block (without friction)

Here's a simple problem:

1. set up a track on your table so that it is tilted at an angle of 27 degrees
2. place a friction block on the track, fabric-side down
3. let the block slide down the track a distance 80 cm

How long will it take the block to slide that distance?

• Make a diagram of the situation.
• Draw a free-body diagram of the block
• Make a table showing all the forces acting on the block
• Determine the block's acceleration down the track
• Compute the time it should take to slide the given distance, assuming there is no friction

Write down your work on a piece of paper. Hand the paper to an instructor.

Then, and only then, may you perform the experiment. Calculate the actual acceleration of the block down the track.

How does the actual acceleration of the block compare to the theoretical value?

If you have time ... Does the condition of the track affect your result? Clean your track gently with paper towels, then repeat the experiment. Do you find the same acceleration? What sort of uncertainty should you attach to your measured acceleration?