Question

What if the moment of the force calculated about the axis of rolling is negative?

(a) It means that the force is applied in the opposite direction as imagined

(b) It means that the direction of the motion is in the opposite sense as imagined

(c) It means that the radius vector is in the opposite sense as imagined

(d) Such calculation means that the calculations are wrongly done

I had been asked this question in examination.

The origin of the question is Rolling Resistance in section Friction of Engineering Mechanics

Answer 1

Right choice is (b) It means that the direction of the motion is in the opposite sense as imagined

To elaborate: It means that the direction of the rolling is in the opposite sense as imagined. We can’t say about the direction of the force or the direction of the radius vector. But yes we can say about the direction of the rolling as it is the thing which is going to be calculated. Rest all the parts are fixed. They can’t be altered.