IIT-JEE 2009 · Paper 1 · Physics Q49

PhysicsMultiple correct+4 / -1Question 49 of 60

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

linear momentum of the system does not change in time

kinetic energy of the system does not change in time

angular momentum of the system does not change in time

potential energy of the system does not change in time

Answer and worked solution

Official answer: A

Zero external force gives $\dfrac{d\vec P}{dt}=0$ : linear momentum is conserved.

Kinetic energy can change (internal forces can do work, e.g. an explosion).
Angular momentum can change if the external forces form a couple (zero net force, nonzero torque).
Potential energy can change through internal forces.

(A)

Topics:Conservation of linear momentum

IIT-JEE 2009 · Paper 1, Physics question 49