A dumbbell has a mass of 5kg and is pulled upwards with a force of 10N but the dumbbell doesn’t move. What is the size of the normal force?

Answer 1

I assume the dumbbell is resting on the ground (you need to state things like this in the question). In this situation, the normal force equals the weight reduced by the upward force.

F_n = mg - (10 N) = (5 kg)(9.8 m/s²) - (10 N) = (49 N) - (10 N) = 39 N