Correct Answer - Option 4 : Both Magnetic and Frictional
CONCEPT:
Mechanical Energy:
- The sum of potential energy and kinetic energy is called mechanical energy.
Conservative Force:
- The force under whose influence the mechanical energy remains conserved is called conservative force.
Example: - Gravitational force is a conservative force. An object at height h of mass m is falling under the influence of gravity. Its potential energy at this height is given as
P = m × g × h
Where g is the acceleration due to gravity.
- At any point at height x during its motion, the sum of potential energy and kinetic energy will remain the same and equal to h.
\(mgh = mgx + \frac{1}{2}mv^2\)
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Conservative Force is path-independent. The gain in potential energy depends upon the initial and final position and not upon the path taken.
- Work done is equal to the change in potential energy of the system.
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Non-Conservative Force: The force under whose influence the mechanical energy does not remain conserved, and some energy is lost in form of heat or sound are called non - conservative forces.
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Frictional force, viscous force, air resistance are some of the examples of non-conservative forces.
EXPLANATION:
Conservative Forces examples
- Apart from gravitational force, the electrostatic force is also conservative.
- Electrostatic potential energy for two charges at distance r is given as
\(E = \frac{k q Q}{r}\)
- q and Q are charges, and r is the distance between them.
- The change in energy here also depends upon the change in position but does not depend upon the path taken.
Non-conservative forces
- The non - conservative forces include frictional force, normal force, etc.
- As stated above, energy is lost in form of heat.
- Frictional force opposes the motion. In the resistance to opposing the motion, mechanical energy is lost.
- The same is the case with viscous forces.
- Magnetic force is also nonconservative as in some cases it depends upon the position.
- The magnetic force is perpendicular to the motion of charged particles, so the work done is always zero.
CONCLUSION:
- Both Magnetic and Frictional forces are nonconservative.
