# Tag Info

## New answers tagged newtonian-mechanics

### Buoyancy basics

The intuitive way to think about these types of buoyancy problems is in terms of the pressure due the heads of the fluids. Starting with the stated set up, the pressure under the ice cube due to the ...
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Accepted

### Why doesn't Car-Parrinello molecular dynamics require an SCF calculation?

It is not entirely true that Car-Parrinello (CP) Molecular Dynamics (MD) doesn't require a self-consistent field (SCF) calculation at all. The method must start close to the SCF solution (actually a ...
1 vote

### Direction of friction of a block moving down a plane

Kinetic friction will always oppose motion, not other forces. A good tip is to always remember friction (kinetic or static) as a force that tries to prevent motion as its only purpose. So, the ...
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1 vote

### Direction of friction of a block moving down a plane

friction will oppose the component of gravity acting along the ramp That's not a given. That's just a consequence of some situations where that force is "trying" to move the block, but ...
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1 vote
Accepted

### Direction of friction of a block moving down a plane

If it’s kinetic (sliding) friction the friction force will act parallel to the surface and opposite to the motion of the block already underway. If it’s static friction the friction force will again ...
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1 vote

### What are the forces that do work when a spring between two masses pulls inwards?

There is no kinetic energy change in the second system (1,2, spring). So there is no net work done, so no need to ask which external forces that do the work. The constituent particles of the system do ...
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### Would a homogeneous rod on a fulcrum oscillate or remain at rest after displacement?

If the rod were perfectly homogenous, infinitely thin, placed on the fulcrum precisely at the midpoint, and the end released without imparting any motion, the rod would theoretically remain at rest in ...
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### Would a homogeneous rod on a fulcrum oscillate or remain at rest after displacement?

If the rod has insignificant thickness, is uniform, and is perfectly balanced about the fulcrum when level, then the weights of the parts on either side of the fulcrum will be equal no matter what the ...
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### A Force Perpendicular to the Velocity changes only the direction of motion?

Why does a force that remains perpendicular to velocity alaways [sic] only change the direction of the motion(circular) [sic] and not induce a velocity in the perpendicular direction??? Suppose the ...
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1 vote

### A Force Perpendicular to the Velocity changes only the direction of motion?

The word 'perpendicular' indicates a force direction that neither adds to nor subtracts from the forward momentum of the object in question. That is where momentum change is only in direction, not ...
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### Vertical Circular Motion ($u$ minimum)

If we have mass $m$ on a string of length $R$, on Earth ($g$), then the potential energy vs standard pendulum angle is: $$U(\theta) = mgR(1-\cos\theta) + C$$ where $C$ is a constant. I want to pick $C$...
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### Conservation of linear vs. angular momentum in two similar cases

*Case 2: The bullet hits at some point along the rod. Here conservation of linear momentum does not apply (it doesn't work) .... It does apply if you expand the system to include the mass of the ...
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### Granular Material Piles on an Inclined Plane

The 'angle of repose' is the limit of stability for a granular pile. A pile that takes on a conical shape according to the angle of repose, has slumped into that shape. Tilting the base under such a ...
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Accepted

### Vertical Circular Motion ($u$ minimum)

For the vertical pendulum, the string will not be taut for speeds at the apex $v < v_c$ where $v_c$ is the minimum speed calculated by letting the tension approach zero. Therefore the bob will ...
1 vote

### Conservation of linear vs. angular momentum in two similar cases

It is a valid question, that in case 1 it seems that momentum shouldn't be conserved due to the horizontal force of the pivot point. The simple answer to this question is that, the pivot point does ...
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### Granular Material Piles on an Inclined Plane

Consider an imaginary inclined plane that passes through a pile. The part of the pile above it is just a normal pile. The question is what happens when such a pile sits on another surface. Piles are ...
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1 vote

### A Force Perpendicular to the Velocity changes only the direction of motion?

change the direction of the motion(circular) and not induce a velocity in the perpendicular direction One thing to be careful of in this context is the phrase “the perpendicular direction”. The ...
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1 vote

### How to understand gyroscopes by using vectors?

About the angular momentum vector: While efficient, the concept of angular momentum vector is itself already a mathematical abstraction. In order to grasp gyroscopic precession we need to see how it ...
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