Emergency, derive or derivative of moment of intertia

AI Thread Summary
The discussion centers on deriving an expression for the moment of inertia of masses at the ends of arms, specifically in terms of length (l), angle (θ), and mass (m). Participants clarify that "derive" in this context means to calculate or express the moment of inertia, not to differentiate. The moment of inertia is expressed as I = 2m(l sin θ)², indicating the relationship between the variables. There is confusion initially about whether the problem requires a derivative, but it is confirmed that a straightforward calculation is needed. The conversation concludes with a sense of relief as clarity is achieved regarding the assignment.
Clairepie
Messages
12
Reaction score
0

Homework Statement


Needs to be in TODAY (yeah I know I am cutting it close!)
Derive an expression for the moment of inertia of the masses at the ends of the arms in terms of l, θ and m
Is the example question asking for the derivative or is it asking to use the terms above in an equation.

Homework Equations


I=MR^2
I=\Gamma\alpha
R=l sin θ


The Attempt at a Solution


I=(mgl)/(d^2θ/d^2t) or I=2m(l sinθ)^2
It's more the term Derive that is bugging me.

Thanks guys
 
Physics news on Phys.org
Derive doesn't mean differentiate. The problem is simply asking you to calculate I.
 
Clairepie said:
Derive an expression for the moment of inertia of the masses at the ends of the arms in terms of l, θ and m
The moment of inertia of what?
Is the example question asking for the derivative or is it asking to use the terms above in an equation.
I'm guessing (since you didn't give the full problem) that they just want you to express the moment of inertia of some body in terms of those quantities. Not take a derivative! Derive = 'come up with'.
 
Thanks, it seems so obvious now! Having a really bad brain fog day & you've both saved my bacon! I have the rest I think,

Thank you again with extra karma your way

(Cognitive dysfunctional) Claire
 
TL;DR Summary: I came across this question from a Sri Lankan A-level textbook. Question - An ice cube with a length of 10 cm is immersed in water at 0 °C. An observer observes the ice cube from the water, and it seems to be 7.75 cm long. If the refractive index of water is 4/3, find the height of the ice cube immersed in the water. I could not understand how the apparent height of the ice cube in the water depends on the height of the ice cube immersed in the water. Does anyone have an...
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