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| Ans: B (Note that the system is taken as the charged particle only. See LN for more discussion.) |
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Ans: A |
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Ans: A (This is how the kinetic energy is ''defined''!) |
The motion of a charged particle in a constant $\vec{B}$
- is time-reversal invariant
- is not time-reversal invariant
This question is an advanced level question. But it is easy to answer, if one keeps in mind the following definition. Time-reversal invariance: if any possible motion played backwards is also a possible motion, then the system is time-reversal invariant.
Ans: B (Note that the system is taken as the charged particle only. See LN for more discussion.)
The motion of a charged particle in a constant $\vec{B}$
- conserves the mechanical energy
- does not conserve the mechanical energy
Ans: A
The work energy “theorem”
The work energy theorem, $\Delta T = W$ where $T$ is the kinetic energy (and $\Delta T = T_2 - T_1$ is its change) and $W$ is the net work done on the particle, is
- always valid (in classical mechanics).
- valid only for conservative forces.
Ans: A (This is how the kinetic energy is defined!)