1Which of these has the same dimensions as momentum?
Momentum and photon momentum both have the dimensions [M L T⁻¹].
MechanicsClass 11, Laws of Motion
Dimensional formula of Momentum
[M L T-1]
Mass times velocity. It has the same dimension as impulse, which is why impulse equals the change in momentum.
How to get the dimensional formula of momentum
- Start from the definition: momentum = mass × velocity.
- velocity = length / time, so velocity is [L] / [T] = [L T-1].
- Put in the dimension of each part: [M] × [L T-1].
- Add the powers of each base quantity: [M L T-1].
Quantities with the dimensions [M L T⁻¹]
Equal dimensions do not make them the same quantity. Compare momentum with the others in the full grid.
Three questions on momentum
2What is the SI unit of momentum?
The SI unit of momentum is the kilogram metre per second (kg m/s).
3Which one has different dimensions from the others?
Thrust is [M L T⁻²]. The other three are all [M L T⁻¹].
An equation that uses momentum
Equation checker
Matching dimensions are necessary, not sufficient. A check cannot see pure numbers such as 1/2 or 2π, so a consistent equation can still be wrong.
Read as
p = m vp[M L T-1]=mv[M L T-1]Dimensionally consistentEvery term is [M L T-1]
v = velocity
Momentum: quick answers
What is the dimensional formula of momentum?
The dimensional formula of momentum is [M L T⁻¹]. It comes from momentum = mass × velocity.
What is the SI unit of momentum?
The SI unit of momentum is the kilogram metre per second (kg m/s).
Which quantities have the same dimensions as momentum?
Momentum shares [M L T⁻¹] with impulse, photon momentum. Equal dimensions do not make them the same quantity.