Wrote general equation for a free body diagram

AI Thread Summary
A derived equation for the net force and acceleration of a motorcycle on a flat surface is presented, expressed as ƩF = Fp - μ*Fn - FD, where Fp is the force acting against the ground, FD represents air drag, and μ*Fn is the frictional force. The equation is proposed to be applicable to any rolling object, leading to discussions about its limitations, particularly for irregularly shaped objects like an apple. It is noted that a model would be necessary for complex shapes, and the equation may only be valid for nearly perfect circular surfaces. The conversation highlights the need for caution in applying the equation universally to all rolling objects. Overall, the equation's generality is questioned, emphasizing its applicability to specific scenarios.
Vodkacannon
Messages
40
Reaction score
0
So I derived this equation for the net force/acceleration of a motorcycle on a flat surface. I believe this equation could practically be used for any rolling object.
ƩF = Fp - μ*Fn - FD
Where: FP is the force of the bike acting against the ground, tangent to the ground
FD = \frac{1}{2}pv2CDA (air drag)
μ*Fn is the frictional force of the tires, Fn is the normal force.

Now to find a:

ma = Fp - μFn - FD

a = (Fp - μFn - FD) / m


Is there anything wrong with this?
 
Physics news on Phys.org
Vodkacannon said:
So I derived this equation[/size]
Woah! Let me turn down the volume a bit there:
... for the net force/acceleration of a motorcycle on a flat surface. I believe this equation could practically be used for any rolling object.
ƩF = Fp - μ*Fn - FD
Where: FP is the force of the bike acting against the ground, tangent to the ground
FD = \frac{1}{2}pv2CDA (air drag)
μ*Fn is the frictional force of the tires, Fn is the normal force.

Now to find a:

ma = Fp - μFn - FD

a = (Fp - μFn - FD) / m


Is there anything wrong with this?
So you'd use this for something like a rolling ball? I guess you'd factor in the mass-distribution in one of the F's there ... that is pretty general indeed. How about for irregularly shaped objects like an apple?
 
Your kidding. Irregulaly shaped objects like apples?
Well you would need to run a model of a 3D apple through a simulator. There can't possibly be an equation to model that.
My bad, that's why you can't use this for every rolling object. Only for surfaces that are nearly perfectly circular.
 
Last edited:
How about a regular shaped object then, like a polyhedron?
A hollow sphere with another, much smaller but heavy, solid sphere free to roll inside it?
You did claim that the equation could be "used for any rolling object".
You asked "in there anything wrong with this?"
Now you know.
 

Thread '1:1 versus 2:1 Mechanical Advantage debate'

The rope is tied into the person (the load of 200 pounds) and the rope goes up from the person to a fixed pulley and back down to his hands. He hauls the rope to suspend himself in the air. What is the mechanical advantage of the system? The person will indeed only have to lift half of his body weight (roughly 100 pounds) because he now lessened the load by that same amount. This APPEARS to be a 2:1 because he can hold himself with half the force, but my question is: is that mechanical...
View full post »

Thread 'Newton's first law?'

Some physics textbook writer told me that Newton's first law applies only on bodies that feel no interactions at all. He said that if a body is on rest or moves in constant velocity, there is no external force acting on it. But I have heard another form of the law that says the net force acting on a body must be zero. This means there is interactions involved after all. So which one is correct?
View full post »
Thread 'Beam on an inclined plane'

Thread 'Beam on an inclined plane'

Hello! I have a question regarding a beam on an inclined plane. I was considering a beam resting on two supports attached to an inclined plane. I was almost sure that the lower support must be more loaded. My imagination about this problem is shown in the picture below. Here is how I wrote the condition of equilibrium forces: $$ \begin{cases} F_{g\parallel}=F_{t1}+F_{t2}, \\ F_{g\perp}=F_{r1}+F_{r2} \end{cases}. $$ On the other hand...
View full post »

Similar threads

I Force Generated By Leg Muscles in Free Body Diagrams
Replies
8
Views
2K
I How can you make a free body diagram for someone running then sliding?
Replies
7
Views
2K
Free body diagrams, coordinate systems origin/orientation
Replies
14
Views
3K
How can I draw a free body diagram of a rotating wheel?
Replies
3
Views
4K
What Are the Rules for Drawing a Free Body Diagram?
Replies
5
Views
7K
Free body diagram of a wheel driven by a motor
2
Replies
81
Views
13K
Finding Radial Force from Free Body Diagram
Replies
4
Views
2K
I Can free body diagrams be used if friction at pivot is not negligible?
Replies
3
Views
1K
Understanding Centripetal Force: Definition, Equations & Free Body Diagrams
Replies
1
Views
2K
Free body Diagram of a Plank resting on two Cylinders
Replies
14
Views
3K

Hot Threads

Recent Insights

Back
Top