Calculating dimensions of power

[fran1942]

Homework Statement

Calculate basic dimensions of power using MLT notation.

2. Given information:
E= P*t
E= .5*mass*velocity^2

The Attempt at a Solution

Rearranging E=Pt to P=E/t
a) P = (.5 mass * velocity^2) / seconds * seconds^2
b) P = (.5 kg * metres^2) / seconds^3
c) moving to one line: .5 kg * metres^2 * seconds ^-3

However I know I have the .5 component wrong. It should not be there. Can someone please point out where I have gone wrong ?
Thanks for any help.

 

[Fewmet]

Homework Statement

Calculate basic dimensions of power using MLT notation.

2. Given information:
E= P*t
E= .5*mass*velocity^2

The Attempt at a Solution

Rearranging E=Pt to P=E/t
a) P = (.5 mass * velocity^2) / seconds * seconds^2
b) P = (.5 kg * metres^2) / seconds^3
c) moving to one line: .5 kg * metres^2 * seconds ^-3

However I know I have the .5 component wrong. It should not be there. Can someone please point out where I have gone wrong ?
Thanks for any help.

Energy is the capacity to do work, where work = force * the distance through which the force is applied. The work-energy theorem says that work done to a body equals its change in energy. When the change is energy is manifested as a change in speed, we say the kinetic energy has changed, and the formula of kinetic energy is 0.5mv².

The easy answer is that you are looking for units, which means you don't need to pay attention to the 0.5. The units of energy are kg*m²/s². But that's not very satisfying.

When the work is done against an attractive or repulsive force, we say he potential energy changes. PE = mgh.

You could avoid introducing the 0.5 by starting with the formula for work or for potential energy.

 

[Redbelly98]

Simple, quick answer: when you're just figuring out units, ignore the numbers in the formula.

Simple example:

diameter = 2 x radius​

Both diameter and radius are measured in meters. We do not say that if the radius is measured in m, then the diameter must be measured in units of 2 m.