Question 3
In activity 03 a block whose length, breadth and height are all different is stood in turn on face A, face B and face C, all covered with sandpaper of the same roughness. How do the limiting frictions compare?
The right answer is the one marked above.
The same for all three faces. The area of the contact surfaces makes no difference to friction.
"Largest for the largest face" is what almost everyone predicts before doing the experiment. The reading on the balance simply does not agree.