Check the dimensional correctness of v² = u² + 2as
Third equation of motion. Links the speeds to the distance covered, with time left out.
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.
v2 = u2 + 2 a sv2[L2 T-2]=u2[L2 T-2]+2as[L2 T-2]Step by step
1. What each symbol stands for
- v velocity [L T-1]
- u velocity [L T-1]
- a acceleration [L T-2]
- s displacement [L]
2. The dimensions of each term
- v2 [L T-1]2 [L2 T-2]
- u2 [L T-1]2 [L2 T-2]
- +2as 2 × [L T-2] × [L] [L2 T-2]
3. Compare
Every term has dimensions [L2 T-2], so the equation is dimensionally consistent.
What it proves and what it does not
It can show
- Every term that is added or subtracted has the same dimensions, so the sum makes sense.
- Both sides of the equals sign have the same dimensions.
- Angles inside sin, cos and similar functions are pure numbers.
It cannot show
- A pure number such as 1/2 or 2π has no dimensions, so a check cannot see a missing or wrong one.
- Two quantities with the same dimensions, such as work and torque, cannot be told apart.
- A sign error or a wrong power that keeps the dimensions equal goes unnoticed.
Matching dimensions are necessary but not sufficient. Pure numbers such as 1/2 or 2π have no dimensions, so a check cannot see them, and an equation with matching dimensions can still be wrong.
Look up each quantity
v² = u² + 2as: quick answers
Is v² = u² + 2as dimensionally correct?
Yes. Every term has the same dimensions, [L² T⁻²], so v² = u² + 2as is dimensionally consistent. That does not prove the equation itself is correct.
Does a dimension check prove v² = u² + 2as is right?
No. A check can show that an equation is wrong, but it cannot show that it is right. Pure numbers such as 1/2 and 2π have no dimensions, so the check cannot see them.