Question 6
A block of weight 50 N rests on a horizontal table, and a 30 N weight is then placed on top of it. What is the new normal reaction of the table on the block, and what happens to the limiting friction?
The right answer is the one marked above.
80 N, and the limiting friction increases.
R = 50 + 30 = 80 N
Limiting friction rises with the normal reaction, which is what activity 04 showed by stacking blocks. Note the surfaces in contact and their area are both unchanged — R is the only thing that moved.