Solving circular motion problem

AI Thread Summary
The discussion centers on understanding the variables in two physics equations related to circular motion. The first equation, Fc = Mr(θ - θ0)² / (t - tn)², is identified as calculating centripetal force, with Fc representing this force, Mr as mass times radius, and θ as angular position. The second equation, M = Fk / (Mk * m * g * cos(θ)), involves kinetic friction and requires clarification on the variables involved, particularly M and Mk. Participants emphasize the importance of knowing which variables are inputs and which are outputs in order to effectively use the equations in a computer program. The conversation concludes with a focus on the need for clarity in the problem statement and the relationships between the variables.
SnoppDoge
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Homework Statement



Our teacher gave us a formula to solve it by creating a computer program but the problem is I'm not good at physics. I need to know what is Fc,Mr,Fk etc..

1.) Fc = Mr(theta - Oo) ^ 2 / (t - tn) ^ 2

2.) M = Fk / Mk(m)(g)cos(theta)

Homework Equations

The Attempt at a Solution


I tried to google my formula but end up nothing so i registered here.

I already created the computer program to solve it i just assigned a value for them but i need to know what am i solving for, e.g r is the radius, m is the mass
 
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SnoppDoge said:

Homework Statement



Our teacher gave us a formula to solve it by creating a computer program but the problem is I'm not good at physics. I need to know what is Fc,Mr,Fk etc..

1.) Fc = Mr(theta - Oo) ^ 2 / (t - tn) ^ 2

2.) M = Fk / Mk(m)(g)cos(theta)

Homework Equations

The Attempt at a Solution


I tried to google my formula but end up nothing so i registered here.

I already created the computer program to solve it i just assigned a value for them but i need to know what am i solving for, e.g r is the radius, m is the mass
Welcome to the PF. :smile:

Please post the exact problem statement. As you have written it out so far, we would just be guessing. Also, I've changed your thread title to be more descriptive of the problem you are asking about. Please try to use very descriptive thread titles here. Thanks.
 
SnoppDoge said:
Our teacher gave us a formula to solve it by creating a computer program
In principle, you do not need to have any idea what the variables represent in order to write a program to solve an equation. But you do need to know which are the inputs and which are the unknowns to be calculated.
From your post, it is not entirely clear to me how many variables there are. E.g. is Mr one variable or the product of two variables, M and r? I suspect the statement of the problem given to you makes that clear, but it has been lost in the way you have typed it out. Please use subscripts and superscripts as appropriate (use the X2 and X2 buttons in the toolbar).
The Oo looks rather unlikely. Is this perhaps a Greek character? You can get theta etc. and some special symbols from the ∑ button in the toolbar.
 
1.) Fc = Mr( - 00)2 / (t - tn)2

in number 1 it's solving for Fc <- i don't know what is Fc

2.) m = Fk / Mk(m)(g)cos(theta)

in number 2 it's solving for m

i can't find a symbol for a theta, but this is the closest symbol for theta: ∅
 
SnoppDoge said:
in number 1 it's solving for Fc <- i don't know what is Fc
Why do you care? If you are given inputs Mr, 00 (or do you mean O0?), t and tn, it seems simple to calculate Fc. I have the feeling you have not fully explained your task.
SnoppDoge said:
in number 2 it's solving for m
Is the equation m = Fk / (Mk(m)(g)cos(theta))? And does "Mk(m)" mean Mk multiplied by m or that Mk is a function of m? If it means multiplied by, you need to rework the equation so that m only appears on one side.
 
No Mk(m) means multiply and it's not a function of m

and what is Fc is it force? and what is m in number 2? is it mass?
 
SnoppDoge said:
what is Fc is it force?
There is no way anyone on the Forum can tell for sure, we can only guess.
Fc is sometimes used for centripetal force. If so, I can try to make sense of the rest of the equation, which you originally posted as:
SnoppDoge said:
Fc = Mr(theta - Oo) ^ 2 / (t - tn) ^ 2
You later put that r as a subscript, but I suspect that was wrong. It's probably a radius.
The Oo could be θ0, an initial angle. The tn maybe t0, an initial time. That gives us
Fc=Mr(θ-θ0)2/(t-t0)2.
That makes sense if a (small) object mass M is rotating at distance r from an axis at constant speed and moves from an angular position θ0 at time t0 to θ at time t. The formula would give the centripetal force required.
SnoppDoge said:
what is m in number 2? is it mass?
Almost surely.
You originally posted this as
SnoppDoge said:
M = Fk / Mk(m)(g)cos(theta)
When you put in subscripts you changed it to
SnoppDoge said:
m = Fk / Mk(m)(g)cos(theta)
which resulted in the variable m appearing on both sides. I now assume you mean either ##M = \frac{F_k}{M_kmg\cos(\theta)}## or ##M = \frac{F_k}{M_k}mg\cos(\theta)##. Neither makes obvious sense. Fk smells like a force, maybe of kinetic friction. mg cos(θ) would also be a force. Not sure what M and Mk are supposed to be, but one would guess they are of the same type.
If ##M = \frac{F_k}{M_kmg\cos(\theta)}## then ##M M_k= \frac{F_k}{mg\cos(\theta)}##, making the M's dimensionless.
If ##M = \frac{F_k}{M_k}mg\cos(\theta)## then ##M M_k= F_kmg\cos(\theta)##, making the Ms also forces.
 
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haruspex said:
There is no way anyone on the Forum can tell for sure, we can only guess.
Fc is sometimes used for centripetal force. If so, I can try to make sense of the rest of the equation, which you originally posted as:

You later put that r as a subscript, but I suspect that was wrong. It's probably a radius.
The Oo could be θ0, an initial angle. The tn maybe t0, an initial time. That gives us
Fc=Mr(θ-θ0)2/(t-t0)2.
That makes sense if a (small) object mass M is rotating at distance r from an axis at constant speed and moves from an angular position θ0 at time t0 to θ at time t. The formula would give the centripetal force required.

Almost surely.
You originally posted this as

When you put in subscripts you changed it to

which resulted in the variable m appearing on both sides. I now assume you mean either ##M = \frac{F_k}{M_kmg\cos(\theta)}## or ##M = \frac{F_k}{M_k}mg\cos(\theta)##. Neither makes obvious sense. Fk smells like a force, maybe of kinetic friction. mg cos(θ) would also be a force. Not sure what M and Mk are supposed to be, but one would guess they are of the same type.
If ##M = \frac{F_k}{M_kmg\cos(\theta)}## then ##M M_k= \frac{F_k}{mg\cos(\theta)}##, making the M's dimensionless.
If ##M = \frac{F_k}{M_k}mg\cos(\theta)## then ##M M_k= F_kmg\cos(\theta)##, making the Ms also forces.
Thank you sir! and that explains my problem!
haruspex said:
Fc=Mr(θ-θ0)2/(t-t0)2

Kinetic Friction and Centripetal Force is what i need. Thanks a lot!
 
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