Question

There is a block A on the car B. The weight of the block A and car B are 5 N and 10 N respectively. You are pulling the block A with force F = 0.8 N. The maximum value of the static friction on A is 1 N. The maximum value of the rolling friction on the car B is 0.2 N. Find the net force on the system(i.e. A and car B)?

• A.
  1.0 N
• B.
  0.6 N
• C.
  0.2 N
• D.
  1.2 N

Answer 1

The correct option is B

0.6 N
Maximum friction between block A and car B(1 N) is always greater than the maximum friction between ground and car B(0.2 N). So after applying 0.8 N force to the block A, it will not move with respect to car B. So both the system will move together. On the car B 0.2 N rolling friction is acting and it is opposite to F. So, net force on the system(i.e. block A and car B) will be
$F_{net}$ = (F - 0.2) N
= (0.8 - 0.2) N
= 0.6 N