All external forces on the body cancel out. Which statement must be correct?
A The body doesn't move.
B the momentum of the body remains unchanged.
C The speed of the body remains unchanged.
D The total energy ( kinetic and potential ) pf the body remains unchanged.
Give reasons for your answer.
A The body doesn't move.
B the momentum of the body remains unchanged.
C The speed of the body remains unchanged.
D The total energy ( kinetic and potential ) pf the body remains unchanged.
Give reasons for your answer.
2 Answers
Explanation:
As there is no external force acting on the body, the momentum remains conserved (in whichever direction the external force is absent).
Obviously not A...
Explanation:
A is incorrect. If all external forces on the body cancel out, the body may be moving with a constant velocity with
B is correct. Here, the law of conservation of momentum is applied.
C is correct. If the momentum of the body remains unchanged, the speed also doesn't change.
D is correct. The total Mechanical energy ( kinetic + potential ) of the body will remain unchanged.
EDIT: (After the comment by @UmAir Ansar)
C is correct, if nothing else changes (mentioned above) . But if the mass of the body is changing , (like a rocket ejecting some of its fuel) the speed of the body will change. So, C can be considered
D can be considered
So, we can conclude that B is the only consistent statement here, which does not contradict anything else. So B is the