Wrote general equation for a free body diagram

In summary, the conversation discusses an equation derived for the net force/acceleration of a motorcycle on a flat surface, which can also be applied to other rolling objects. The equation takes into account the force of the bike against the ground, frictional force of the tires, and air drag. The conversation also brings up the possibility of using the equation for irregularly shaped objects and clarifies that it is only applicable to nearly perfect circular surfaces. Additionally, there is a discussion about using the equation for a hollow sphere with a smaller solid sphere inside, and the limitations of the equation for non-circular surfaces.
  • #1
Vodkacannon
40
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 = [itex]\frac{1}{2}[/itex]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?
 
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  • #2
Vodkacannon said:
So I derived this equation
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 = [itex]\frac{1}{2}[/itex]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?
 
  • #3
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:
  • #4
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.
 
  • #5


I would say that your equation looks accurate and comprehensive for describing the net force/acceleration of a motorcycle on a flat surface. It takes into account the various forces acting on the motorcycle, including the force of the bike itself, friction from the tires, and air drag. I agree that this equation could potentially be applied to other rolling objects as well, as long as the factors such as air resistance and friction are considered. However, it is always important to test and validate any equations through experimentation and observation, as there may be other factors at play that could affect the motion of the object.
 

What is a free body diagram?

A free body diagram is a visual representation of all the forces acting on an object in a given system. It helps to analyze and understand the motion or equilibrium of the object.

Why is it important to write a general equation for a free body diagram?

Writing a general equation for a free body diagram allows us to mathematically represent the forces acting on an object. This helps in solving problems and predicting the behavior of the object in the given system.

What are the steps to writing a general equation for a free body diagram?

The steps to writing a general equation for a free body diagram are: 1) Identify the object and all the forces acting on it, 2) Draw the diagram with the object at the center, 3) Label all the forces and their directions, 4) Write down the equations for each force, and 5) Solve the equations to determine the net force on the object.

What are some common forces included in a free body diagram?

Some common forces included in a free body diagram are gravity, normal force, friction, tension, and applied forces. Other forces such as air resistance or buoyancy may also be included depending on the situation.

How can a free body diagram be used to solve real-world problems?

A free body diagram is a useful tool in solving real-world problems involving forces and motion. By representing all the forces acting on an object, we can use the equations to determine the net force and predict the behavior of the object. This is useful in fields such as engineering, physics, and mechanics.

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