Question

Why option C and D are incorrect in the folllowing question ? If the resultant of all the external forces acting on a system of particles is zero, then from an inertial frame, one can surely say that (A) linear momentum of the system does not change in time (B) kinetic energy of the system does not change in time (C) angular momentum of the system does not change in time (D) potential energy of the system does not change in time

Answer 1

Only A is correct.

Answer 2

by work energy thereom we can rule out B and D
as for c even if total force is zero torque acting may not be zero
For example if two equal and opposite forces are acting on the periphery (on two edges of a diameter) of a rim, in this case net force is zero but torque is not.
hence option C is ruled out

Answer 3

yes a is correct

Answer 4

option c is incorrect due to the possibility if external force being equal to 0 even when the net torque acting on the body is 0.

Answer 5

well i simply haven't read the Question so far ,, u see Questio should be properly managed

Answer 6

hey actually net force = 0 doesnot mean that linear momentum is constant.... consider for rotational motion here forces r opposite in nature , both r acting on the same body but rotation comes into effect. so torque is not 0 and linear momentum keeps on changing with respect to different positions.... but net force is 0 so clearly optin c is correct and of course d is correct that potential energy is constant unless applied with external force.... am i clear

Answer 7

Quote: "hey actually net force = 0 doesnot mean that linear momentum is constant..."

Well, by writing this, you are contradicting Newton's first law of motion! This cannot be true.