Convert g*cm^2 to kg*m^2: Explanation & Help

AI Thread Summary
To convert a moment of inertia from g*cm^2 to kg*m^2, first recognize that the conversion involves both mass and length squared. The conversion factors are 0.001 kg/g and 0.01 m/cm, which must be squared for the area unit, resulting in a factor of 0.000001 (or 10^-6) when applied to g*cm^2. Therefore, the correct approach is to multiply the initial value by 0.000001 to obtain the equivalent in kg*m^2. This method ensures that units cancel appropriately, allowing for accurate conversion. Understanding these squared conversion factors is crucial for successful unit transformations in physics problems.
azure.hubris
Messages
9
Reaction score
0
Hello,
I need to convert a moment of intertia value given in g*cm^2 to kg*m^2, and was hoping someone could give me a run down of the method behind these kind of conversions. Do I simply assume that since g to kg is a factor 0.001 and cm to m is 0.01, that I can apply a factor of 0.00001 to my initial value? I feel that that method would be fine for say, g*cm to kg*cm, but I'm not sure how to account for the squared dimension. Any help/explanation would be appreciated. Thanks.
 
Physics news on Phys.org
In general when converting units set your quantity to be converted and your conversion factor up as a multiplication of fractions. For example from m/s to cm/s
10 \frac m s * 100 \frac {cm} {m} = 10*100 \frac m s * \frac {cm} {m} = 1000 \frac {cm} s
Note that in this example the m in the numerator cancels the m in the denominator, leaving only cm in the numerator.
 
Last edited:
okay, i see what you mean, I've used that technique before, but the confusion came from two places for me.
1) that I'm dealing with a squared quantity, so would the conversion be 1000cm^2/m^2?
2) that the it's g*cm^2, rather than g/cm^2, leaving me wondering how to actually set up the calculation.

i'm sure it's quite obvious how to do this, but the way i set it up, the units don't cancel out. i need to be certain of this conversion before i can begin to do the problem, since it's for an online assignment for which i have only one attempt. could you possibly lay out how you'd set it up for the case of my calculation? i know it's not usually acceptable to 'give' the solution away in this forum, but the physics of the problem are not a concern, just this one calculation. okay, thanks again for your help.
 
The method is the same just square the conversion factors. So

10m^2 = 10 m^2 * (100 \frac {cm} m)^2 = 10 * 10^4 m^2 \frac {cm^2} {m^2} = 10^5 cm^2
 
thanks for your help!
 
Thread 'Variable mass system : water sprayed into a moving container'
Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
Back
Top