Question

a packing ccrate slides down an incline ramp at constant velocity. Thus we can deduce that
a) a frictional force is acting on it
b) a net downward force is acting on it
c) it may be accelerating
d) it is not acted on by appreciable gravitational force

with a constant velocity isn't there frictional force acting on it so the correct answer would be a)? I do know that d) is wrong.

Answer 1

If the velocity is constant, as given, then there is no net acceleration and so no net force. That eliminates two answers.

Answer 2

I agree: the word net in b) makes it wrong. Velocity is constant.