page5
Friction
Friction is a force which appears when two surfaces move against one another.
Here is a block moving along a table.
Friction always pulls the opposite way to the motion.
1) This diagram is on sheets of paper. Stick one into your book.
2) There is an adjustable ramp. Lower it to horizontal and measure the friction.
3) Repeat this a few times and calculate the average.
4) Write the results into your table. Make sure it's stuck in your book.
5) Calculate how much work is done against friction when you drag the block 30cm.
Write this equation and calculation into your book (use the average force).
Work = Force x Distance, so Drag Work = Average Drag Force x 0.30m
6) Change the angle of the slope to something that's not horizontal.
I have a theory which I want you to either prove or disprove through experiment:
I think that when you have the slope at an angle, any angle, this formula is always true.
Theory: Total Work = Drag Work + Lift Work
6) Write down the theory and add a comment: do you think it is reasonable?
Why or why not?
You calculated Drag Work in part 5.
Now weigh the block (in Newtons).
7) Repeat this experiment for different slopes:
8) Does the theory pass the test?
If not, what do you think is wrong?
Attach a newtonmeter to the block and pull it with gradually increasing force.
Once the block is moving, use just enough force to keep it moving.
Measure this force as accurately as you can.
Measure the vertical height of the 30cm mark.
Calculate and write it in your results table
Lift Work = Force x Distance = weight x height
Repeat the test in step 2 for this new slope.
Calculate and write in your results table:
Total Work = Newly Measured Force x 0.3m
Add Lift Work to the Drag Work from step 5.
motion
friction
30cm
height
1st Result
2nd Result
3rd Result
Range
(max - min)
Mean
(average)
Force (N)
Height
(m)
Lift Work
(J)
Lift Work
+
Drag Work
(J)
Total Work
(J)