- #1
Cyrus Hafezparast
- 2
- 1
So there was a really old thread about this, but I don't think the matter was ever really resolved, which is why I'm making this thread now.
I'm trying to derive the equation τ = Fd but I've run into a bit of trouble. I started with x=θr where x is the arclength on a circle (since any point on a rotating rigid body is going to follow a circular path) and then, from that, v=ωr and differentiating again to a=r(dθ/dt) . Now multiple by m on both sides and you have
ma=rm(dθ/dt)
∴F=r τ [Perhaps this is the source of my error, but I'm taking f=ma as general and applying it to mass times angular acceleration to give angular force (Torque)]
Which is not what we wanted at all!
(PS I'm new to the forum, I made an account just for this question, so I realize that my formatting needs work, I couldn't easily see how to write the derivative nicely as a fraction like I've seen in other threads, I couldn't decide whether to write my working line by line or not etc etc, please be nice XD I also didn't know which prefix to use, but where I live there's no calculus in our high school physics course and most people in my classes aren't really questioning to this extent, so I thought I'd put Intermediate)
I'm trying to derive the equation τ = Fd but I've run into a bit of trouble. I started with x=θr where x is the arclength on a circle (since any point on a rotating rigid body is going to follow a circular path) and then, from that, v=ωr and differentiating again to a=r(dθ/dt) . Now multiple by m on both sides and you have
ma=rm(dθ/dt)
∴F=r τ [Perhaps this is the source of my error, but I'm taking f=ma as general and applying it to mass times angular acceleration to give angular force (Torque)]
Which is not what we wanted at all!
(PS I'm new to the forum, I made an account just for this question, so I realize that my formatting needs work, I couldn't easily see how to write the derivative nicely as a fraction like I've seen in other threads, I couldn't decide whether to write my working line by line or not etc etc, please be nice XD I also didn't know which prefix to use, but where I live there's no calculus in our high school physics course and most people in my classes aren't really questioning to this extent, so I thought I'd put Intermediate)