Question

$Joule\times second$ is the unit of

• A. Energy
• B. Momentum
• C. Angular momentum
• D. Power

Answer 1

The correct option is C Angular momentum

Joule is a unit of energy and second is the unit of time.

Thus, $Joule\times second$ has dimensions $M{L}^2{T}^{-2}\times T=M{L}^2{T}^{-1}$
Now, energy cannot be the answer since energy has Joule as its unit and cannot be Joule-seconds.
Momentum can't be the answer as momentum is force X time which has dimensions $ML{T}^{-1}$
Angular momentum is given by cross product of linear momentum and radius vector thus it has dimensions $ML{T}^{-1}\times L=M{L}^2{T}^{-1}$, which is the correct answer.
Finally, Power is force times velocity, so its dimensions are $ML{T}^{-2}\times L{T}^{-1}=M{L}^2{T}^{-3}$