Question

If forces are acting on a rigid body so that it has zero kinetic energy, then all forces will pass through the centre of mass and have a vector sum of zero. True or False?

(a) True

(b) False

This question was addressed to me in final exam.

My question is from System of Particles topic in portion System of Particles and Rotational Motion of Physics – Class 11

Answer 1

Right option is (b) False

The explanation: If a rigid body has zero kinetic energy means that vector sum of all forces will be zero and the torque on it will be zero. For torque to be zero the vector cross product of force and distance should be zero. It is not necessary for all forces to pass through the centre.