Question

You slide an 800 N table across the kitchen floor by pushing with a force of 100 N. If the table moves at a constant speed, the friction force with the floor must be

a. 800 N.

b. greater than 100 N but less than 800 N.

c. greater than 800 N.

d. 100 N.

Answer 1

The Newton's second law says

$$ma=F_{net}=F-F_f$$

When $v=const$ then $a=0$.

Hence

$$F_f=F$$

Answer: d. 100 N.