TPR Dumb Physics Question

[puravida85]

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This question really pisses me off because it's erroneous in the way it's stated and because it undermines our algebraic ability.

TPR Hyperlearning Kinematics Practice Question:

7. The work done in pushing an object of mass m (in kg) from rest to speed v (m/s) is given by W = mv^2/2. Find the SI unit for work.

My Side Note: The portion of these practice questions is to take the formula for work (mv^2/2) and derive the units for work which we all know to be kg*m^2/s^2 = joule.

If you didn't already know that, it's impossible to blindly derive it from mv^2/2. This equation is derived from v^2= vnot^2 + 2 ad. Plugging in F/m for a and turning initial velocity to 0 because of the object starts at rest, you get:

2 *(f/m) *d = v^2
With algebra you eventually get:

F*d = 1/2 m v^2 = W

That's what I know off hand.

But if you tried to blindly derive the units for 1/2mv^2 you would just get

(kg*m^2/s^2)/2 = W. How the hell would you get rid of the 1/2 without ruining the true nature of the units. I hate dumb questions. Sorry just hand to rant about it cause I spent like half an hour trying to think about a way to derive it.

 

[Isoprop]

But if you tried to blindly derive the units for 1/2mv^2 you would just get

(kg*m^2/s^2)/2 = W. How the hell would you get rid of the 1/2 without ruining the true nature of the units. I hate dumb questions. Sorry just hand to rant about it cause I spent like half an hour trying to think about a way to derive it.

the "1/2" is unitless. So the units would be [kg][m/s]^2 = [kg][m]^2/^2 = [Joule]