Conservative Force Identification
A force is defined as conservative if the work done by it moving an object between two points is independent of the path taken. The work done by a conservative force over any closed path is always zero. Potential energy can be associated with conservative forces.
Analyzing the Options
- Frictional force: This is a non-conservative force. The work done depends on the distance traveled and opposes motion, converting energy into heat.
- Air resistance: Similar to friction, this is a non-conservative force. It opposes motion through the air, and the work done depends on the path and speed.
- Electrostatic force: This is a conservative force. The work done by electrostatic forces (like between charges) depends only on the initial and final positions, not the path followed. It is associated with electric potential energy.
- Viscous force: This is also a non-conservative force, acting like fluid friction. It opposes motion through a fluid, and the work done is path-dependent.
Therefore, the only conservative force among the options is the electrostatic force.
Important Questions from Common forces in mechanics
Which of the following is NOT true about Frictional force?
A. Friction is the force which opposes the relative motion of two surfaces in contact.
B. The force of friction that acts when a body is moving (sliding) on a surface is called sliding friction.
C. Friction in machines wastes energy and also causes wear and tear.
D. Rolling friction is much more than sliding friction, the use of ball bearings in a machine considerably reduces friction.
Which of the following is a wrong example of friction?
Which one of the following statements about friction is incorrect?
- An electric lift with a maximum load of $2000\text{ kg}$ (lift + passengers) starts from rest and accelerates upwards at $0.2\text{ ms}^{-2}$. The frictional force opposing the motion is $3000\text{ N}$. The instantaneous power delivered by the motor when the lift reaches a speed of $1.5\text{ ms}^{-1}$ is:
(Assume $g = 10\text{ ms}^{-2}$) When a wheel is rolling on a level road, the direction of frictional force between the wheel and road is in:
