17) Work done by the force of friction is: (Work, Power & Energy, work done by constant and variable forces)
Correct answer: B. always negative
- A. always positive
- B. always negative
- C. positive only for small frictional force
- D. positive only for large frictional force
Explanation
Correct Answer: (b) always negativeExplanation: Friction is a non-conservative force, meaning it dissipates energy as heat. Therefore, the work done by friction is always against the direction of motion, leading to a decrease in the kinetic energy of the object. This translates to negative work done by friction. Incorrect Options:(a) Always positive: Frictional work is always negative, as it opposes movement and reduces kinetic energy.(c) Positive only for small frictional force: This statement is not true. Friction always dissipates energy regardless of its magnitude.(d) Positive only for large frictional force: Similar to option (c), this is incorrect. The direction of work done by friction is independent of its strength, and it always opposes movement.
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About Work and Energy
Work transfers energy when a force causes displacement, while kinetic energy, gravitational potential energy and power describe motion, position and the rate of energy transfer. The work-energy theorem links net work with change in kinetic energy, and efficiency accounts for energy losses rather than treating them as energy destruction.
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