MCQ practice · SSC Physics Board questions · Chapter 4: Work, Power and Energy
Which is the unit of power?
Think it through first, then pick an option.
- a kg m²s⁻³
- b kg m²s⁻²
- c kg ms⁻²
- d kg m⁻¹ s⁻²
Answer and explanation
Correct answer: a kg m²s⁻³
The dimension of power is ML²T⁻³, so the unit is kg m² s⁻³ (= W = J/s). kg m² s⁻² is the unit of energy, kg m s⁻² of force and kg m⁻¹ s⁻² of pressure.
Why the other options are wrong
- b kg m²s⁻²: This is not the answer: The dimension of power is ML²T⁻³, so the unit is kg m² s⁻³ (= W = J/s). kg m² s⁻² is the unit of energy, kg m s⁻² of force and kg m⁻¹ s⁻² of pressure.
- c kg ms⁻²: This is not the answer: The dimension of power is ML²T⁻³, so the unit is kg m² s⁻³ (= W = J/s). kg m² s⁻² is the unit of energy, kg m s⁻² of force and kg m⁻¹ s⁻² of pressure.
- d kg m⁻¹ s⁻²: This is not the answer: The dimension of power is ML²T⁻³, so the unit is kg m² s⁻³ (= W = J/s). kg m² s⁻² is the unit of energy, kg m s⁻² of force and kg m⁻¹ s⁻² of pressure.
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