# Questions tagged [newtonian-mechanics]

Newtonian mechanics covers the discussion of the movement of classical bodies under the influence of forces by making use of Newton’s three laws. For more general concepts, use [classical-mechanics]. For Newton’s description of gravity, use [newtonian-gravity].

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### If the net external moment on a body about a point is zero

I was told that If net external moment of some forces is zero about a point, then the net external force passes through the point. I know it's not true in general, what was the special condition ...
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### How do you calculate the distance from center for centripetal force equation for long objects such as board or a hammer?

I am trying to calculate the centripetal force for an enlongated object like a fan blade. Where do I measure to to get the distance from center. Would I measure from the center to the end of the ...
25 votes
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### Is it correct to say that it is theoretically impossible for perfect rigid bodies to exist?

If perfect rigid bodies were to exist, then consider a scenario in which two rigid bodies of equal masses moving with velocities of equal magnitude but opposite in direction colliding against one ...
2 votes
1 answer
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### Dropped ball entering curved surface: Bounce or not?

Referencing this question here of a ball being dropped onto the end of a curved bowl: Velocity of ball sliding on bowl. Need to understand why vertical velocity of bowl is 0 and ball is not What is ...
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1 answer
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### Rotation of a rigid body

I am dealing with the motion of rigid bodies and in studying it I came up with some questions about the nature of rotation. (1) Does a rotation always have to happen about one fixed axis? (2) Is ...
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1 answer
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### Wind Power in a Wind Tunnel

Two questions in one day! What? Okay, so the power equation for air flow is as follows: $$P = 1/2 \cdot \rho \cdot A \cdot V^3$$ In a wind tunnel due to the Bernoulli principle as the area ($A$) ...
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1 answer
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### End motion of an empty spherical shell with a ball rolling on it's inner surface

Let's picture an empty sperical shell in inter galactic space or beyond. Inside this shell, a ball is rolling on the inner surface. Because of friction and the centrifugal force the ball exerts on the ...
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1 answer
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### Slip definition that works in game

Wikipedia article gives us the following 2 equations: $$\%_{slip} = \frac{\omega r - v}{|v|} * 100$$ (The use of $v$ modulus makes it work in all directions. It is multiplied by 100 to get the ...
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### Which one is better for robotic arm: planetary gear VS pully and pinion? [closed]

I have been watching different DIY robotic arm builds on youtube, most use either planetary gear or pully and pinion. what would be the advantages of using one over the other?
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### Is there a function or equation that can trace the trajectory of a space rocket's motion on the three coordinate axes $(x ,y ,z)$?

To be honest I'm working on a project at the university which is a simulation of launching a rocket into space The problem here is that this simulation needs to be realistic enough for my programming ...
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### A question regarding work done by tension force in a simple pendulum

Consider the picture given below to show the free body diagram of a simple pendulum going to and fro and not a conical pendulum. I have read in my physics book that work done by tension force is zero ...
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### Can an object move with a constant velocity without balanced forces?

Can an object move with a constant (magnitude) velocity without the balanced forces? As an object which is balanced with the frictional force continues moving at a constant velocity, acquired till ...
2 votes
2 answers
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### Doubts about direction of normal contact force acting on a tilted rod supported by another body

I'm confused about the direction of the normal contact force acting on a body supported by another body. I have read the following : If a body is being supported by a surface, the normal force acting ...
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### Differential equations of a forced coupled spring-pendulum system

Currently working on a problem and I can really figure out how to write the differential equations for it. Here's the situation: So we have a mass $m$ tied to the wall with a spring of constant $k$. ...
10 votes
1 answer
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### The Role of the Virtual Work Principle

Lanczos' masterpiece "The Variational Principle of Mechanics" has, on page 76, the following statement: Postulate A (virtual work): The virtual work of the forces of reaction is always zero for any ...
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### Force exerted on ground from a slipping wheel

I am trying to do some car calculations for a game. I have a tyre (radius $r$, inertia $I$) rotating around it's axle with an angular velocity $\omega$ faster than the center of mass is moving across ...
2 votes
3 answers
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### Do electrons have inertia?

I don't know quantum mechanics and know a little bit about mechanics and a very little bit about subatomic particles but I am just a curious to know the answer to my question. My question is if '...
1 vote
3 answers
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### Acceleration of free fall at different parts of Earth

“free fall is any motion of a body where gravity is the only acceleration acting upon it.” -Wikipedia Question 1 - If an object is falling freely, will it follow the Earth’s rotation too? Or will ...
11 votes
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### Is friction required for knots (not hitches or bends) to hold fast to a rope?

Using rope with idealized coefficient of surface friction approaching zero, that is in all other ways typical (typically stretchable, compressible, flexible and twistable), is it possible to tighten a ...
22 votes
7 answers
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### On general covariance

If newton's theory could be formulated in the language of differential geometry (symplectic manifolds), what do we really mean when we say that the theory is covariant under the Galilean group when it'...