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