A mass m is moving with a constant velocity along a line parallel to the x-axis, away from the origin. Its angular momentum with respect to the origin?
A.
Is zero
B.
Remains constant
C.
Goes on increasing
D.
Goes on decreasing
Answer: Option B
Explanation:
Angular momentum = Mass of momentum L = mv×h = constant As the particle moves, m, v and h all remain unchanged.
A particles undergoes uniform circular motion. About which point on the plane of the circle, will the angular momentum of the particles remain conserved?
A.
Centre of the circle
B.
On the circumference of the circle
C.
Inside the circle
D.
Outside the circle
Answer: Option A
Explanation:
In uniform circular motion, centripetal force acts towards the centre. Torque due to such a force about the centre is zero. Hence the angular momentum is conserved about the centre of the circle.
If the resultant of all the external forces acting on a system of particles is 0, 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: Option A
Explanation:
According to the law of conservation of linear momentum if external force is 0 then the linear momentum of the system does not change in time. There may be external forces acting due to which kinetic energy or potential energy or both may change. Also, net force is 0 does not mean net torque is 0. So angular momentum may change. Hence only linear momentum of the system does not change in time.
