Question

How to convert 80kgm2sec-1into j-min?

Answer 1

With dimensional analysis!

`(80kg*m^2)/s * (J)/((kg*m^2)/s^2) * (min)/(60s) approx 1.33J*min`

This makes the case for why units are very important in chemistry and physics.

Answer 2

`80kgm^2sec^-1 = 1.33 J*"min"`

Explanation:

You have `80kgm^2sec^-1`. The units that they asked you to convert that to, `J*min`, looks like work times time. Allow me to rewrite `80kgm^2s^-1` this way:

`80 kg*(m*m)/s`.

The reason for doing that will become clear.

Newton's 2nd Law, F= m*a, will convince you that the Newton is equivalent to `kg*m/s^2`. Now I will continue to rewrite the original. Now I will rewrite the latest --`80 kg*(m*m)/s`.

`80 kg*(m*m*s)/s^2`

I hope you are following this. That last is an equivalent to the `80kgm^2sec^-1` that you started with.

Now I will group some of the individual units so that I can get Newton*meters, which would be equivalent to Joules. From that last rewrite, check this out:

`80 kg*m/(s^2)*m*s = 80 N*m*s = 80 J*s`

Now we have units of Joule*second. The only thing remaining is to change those seconds to minutes.

`80 J*s * (1 min)/(60 s) = 1.33 J*"min"`

I hope this helps,
Steve