A dimensionally correct equation need not actually be a correct equation but dimensionally incorrect equation is necessarily wrong. Justify.
(i) To justify a dimensionally correct equation need not be actually a correct equation,
consider equation, v2 = 2as
Dimensions of L.H.S. = [v2] = [L2M0T2]
Dimensions of R.H.S. = [as]= [L2M0T2]
⇒ [L.H.S.] = [R.H.S.]
This implies equation v2 = 2as is dimensionally correct.
But actual equation is, v2 = u2 + 2as
This confirms a dimensionally correct equation need not be actually a correct equation.
(ii) To justify dimensionally incorrect equation is necessarily wrong, consider the formula, \(\frac{1}{2}\) mv = mgh
Dimensions of L.H.S. = [mv] = [L1M1T-1]
Dimensions of R.H.S. = [mgh] = [L2M1T-2]
Since the dimensions of R.H.S. and L.H.S. are not equal, the formula given by equation must be incorrect.
This confirms dimensionally incorrect equation is necessarily wrong.