Question

All of the following show friction as a useful force, except _____.
a) the heat energy produced when two surfaces rub together.
b) having to push a rough and heavy box across the floor to move it.
c) the friction between your feet and the floor keeping you from slipping.
d) the tread on tires helping the moving vehicle slow down and stop when necessary.

Answer 1

hello friend here is your answer
.
a) the heat energy produced when two surfaces rub together.

Answer 2

(b) having to push a rough and heavy box across the floor to move it