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 discussion of energy, momentum conservation etc., use classical-mechanics, for Newton’s description of gravity, use newtonian-gravity.

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Trajectory of rolling billiard ball after collision with another billiard ball with same mass

So, according to this article http://www.real-world-physics-problems.com/physics-of-billiards.html , the trajectory of white (cue) ball is always perpendicular to the line connecting center of ball ...
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1answer
112 views

Natural frequencies of a torsion system

Find the angular displacement $\theta_1(t)$ and $\theta_2(t)$ of the system shown in figure below for the initial conditions $\theta_1(0)$, $\theta_2(0)$, and $\dot{\theta}_1(0) = \dot{\theta}_2(0) ...
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6answers
815 views

Why is momentum conserved (or rather what makes an object carry on moving infinitely)?

I know this is an incredibly simple question, but I am trying to find a very simple explanation to this other than the simple logic that energy is conserved when two items impact and bounce off each ...
9
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1answer
2k views

Why don't lakes have tides?

There's a tidal effect that we can clearly observe in oceans, which is the effect of gravity from the Sun and the Moon. If gravity affects everything equally, why don't lakes have tides?
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0answers
40 views

To what depth can a whirlpool descend & would a barrel save you being pulled down?

My question is based around comparing the physics of a tornado against, what I imagine/assume to be the marine equivalent of a tornado, that is a whirlpool located either at sea, in a tidal region or ...
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0answers
14 views

What axial forces does the vertical load induce? [on hold]

What axial forces does the vertical load P induce in the members of the system down in the figure? Neglect there weights of the members themselves and assume an ideal hinge at A and a perfectly ...
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3answers
136 views

Why can this question about Centripetal Force not be answered in this way? [on hold]

Here is the question: "A car travels round a bend which has radius $100~\text{m}$ and is banked at an angle of $20°$ to the horizontal. The car is travelling at a speed of $30 ...
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1answer
49 views

Why is centre of mass taken as integral of x.dm and not m.dx?

Forgive me if I'm being naive, but, I don't understand why the X-coordinate of the Centre of mass is taken as an integral of x.dm and not m.dx. I understand the summation part, but how do we convert ...
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0answers
20 views

Frictional pulley

Whenever we do any pulley problems, generally, it is mentioned, that the pulley is $massless$ and $frictionless$. But, what will happen if it is given that the pulley is frictional. I had gone a ...
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1answer
416 views

Walking and Friction

If walking is a result of the reaction to a kick backwards to the ground (reaction being friction), it appears that it should be true that the kick will have to be less than the kinetic friction ...
4
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1answer
43 views

Without using rotational mechanics, why does a gyroscope precess the direction it does?

When a top is spun, it will precess in some direction, either clockwise or counterclockwise. It's possible to find out which way using $\boldsymbol{\tau} = d\mathbf{L}/dt$ and $\boldsymbol{\tau} = ...
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2answers
86 views

If the force of friction is 20 N for a moving body does acceleration increase with the increase of the mass?

A body is moving and the only force acting on it is the force of friction. If we put another body on this moving body somehow the force of friction will increase; does its acceleration change?
3
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1answer
316 views

Rolling a ball into a cone; what should the forces overall be?

This is my solution to finding angular displacement/velocity/acceleration on cone so far. Consider a cone, with an apex of half-angle $\psi$ pointing down, and a height of $h$. If I roll a ball into ...
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2answers
238 views

Correct terminology for combined kinematic and dynamic state

The kinematic state is defined as the position and orientation in space. The dynamic state is defined as the associated velocities. What is the correct terminology for the combined kinematic and ...
7
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2answers
264 views

Sailing against the wind. Is this a fair model?

I was ruminating the explanations about how boats can sail against the wind (or "into the wind"), and wondered if one could devise a simple mechanical model without hydrodynamics involved. Imagine a ...
0
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2answers
36 views

Pertaining to Newton's laws, how do so many objects acheive perfect equilibrium?

Suppose a light is hanging from a ceiling. Supposedly, the force of tension pulling it up is exactly the same as the force of gravity pulling it down. Why is it that the tension happens to be exactly ...
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2answers
87 views

Why does the ground always push up?

In the example of a bouncy ball being thrown at the ground, at some angle from the normal, $\theta$, we know that the ground will apply a force in the normal direction, causing the ball to rebound at ...
8
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6answers
329 views

Why is a beam reach the fastest point of sail on modern sailboats?

I've heard that a beam reach (perpendicular to the wind) is the fastest point of sail on modern sailboats, but I haven't heard a satisfying explanation of the physics behind the claim. Triangular ...
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2answers
61 views

Very basic question about vector

The vectors $a = (2,-1,-2)$ and $b = (0,-3,4)$ are given. Determine $a$:s parallel and normal vector to $b$. Obviously the parallel vector should be the dot product $a \cdot b$ times the unit vector ...
2
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3answers
81 views

Does acceleration follow the same addition like velocity?

Two frames have relative velocity $u$, but an object in one is initially at rest and in the other has velocity $v$. If it then starts to accelerate, the acceleration measured in both frames is equal. ...
0
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1answer
33 views

Does the mass change for a body with eccentric orbit?

I am a student with a programming and electronics background attempting to recap on orbital mechanics. I would appreciate anyone with a physics specialisation helping me understand where my ignorance ...
2
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2answers
424 views

Does a pivot exert an additional force, normal to the centripetal force, on an object rotating about it?

A thin plank of mass $M$ and length $l$ is pivoted at one end. The plank is released at 60$^{\circ}$ from the vertical. What is the magnitude and direction of the force on the pivot when the plank ...
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1answer
48 views

Probablity Wave and Wavefunction [on hold]

Are wave function and probability wave same? Well I am a bit confused about wavefunctions and probability waves. I read in Fabric of the Cosmos by Brian Greene that they are same. Please help me and ...
0
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0answers
20 views

Is it wrong to equate the net force to the force by the spring to find its maximum expansion?

When I want to find the maximum expansion in a spring, let's say connected to 2 blocks of different masses, and some force is applied on one of them, I find their separate accelerations and then ...
3
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2answers
111 views

Pulley-rope tension question

I'm learning mechanics and I don't understand the following (simple, I guess) concept. Here's a pulley-rope system: The force of tension, as I understand it, is defined as the force exerted on an ...
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0answers
17 views

Calculating stable orbital resonance and other factors into orbits

Firstly here is a brief summary of what I trying to accomplish. From a predetermined total solar system mass , star count in that system, per-star classification and mass I am building a system of ...
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0answers
25 views

The underlying chemical interactions behind torque

I did some searching around, and didn't find any previous topics that address torque in this specific way -- here goes: Say I just have a plain ol' piece of wood -- relatively long in one axis, so it ...
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2answers
42 views

Direction of frictional force

How will I find the direction of frictional force for any kind of motion of a moving object?
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1answer
29 views

A homework problem involving collision [closed]

A bullet of mass 25g is fired horizontally into a ballistic pendulum of mass 5.0 kg ang gets embedded in it If the centre of the pendulum rises by 10cm.Find the speed of bullet My approach: let ...
0
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0answers
22 views

Work done by friction in accelerated frames of reference [on hold]

The problem is: An observer and a vehicle start from rest at the same time, with accelerations $5 ~\rm m/s^2$ and $2 ~\rm m/s^2$ respectively. There's a $2 ~\rm kg$ block on the floor of the ...
2
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5answers
142 views

No need Power to fly ? Paradox [duplicate]

I would like to know how much power I need for magnetic levitation. $$P = Fv.$$ $F = F_g \approx \text{mass} \times 10$, okay. But $v = 0$! I can't believe I need no power to keep an object in the ...
0
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2answers
46 views

How does friction act on a body, if only 2 regions on it are rough? [on hold]

While tackling an Olympiad question, it came to my mind that friction need not act in the same direction at all points on a body. I thought of using integration to evaluate the net frictional force, ...
0
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0answers
18 views

What is the tension at a particular point in this case? [closed]

A mass M is connected to a rope of length l and mass m on which an external force 'F', what is the tension force at A? I am not able to make out too much from that diagram but here's what I got:- ...
0
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3answers
184 views

Forces and acceleration on rotating objects?

Suppose you have an object undergoing uniform circular motion, with force vector pointing towards the center and another force vector tangential. Can it be said that the net force pointing in the ...
2
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1answer
28 views

What is the ratio of the acceleration in the two cases (a) and (b)

What is the ratio of the acceleration in the two cases (a) and (b)? I thought that the ratio would be 1:1 but it my textbook says its 1:3, so can someone explain to me how that's possible.
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3answers
970 views

Can you punch a hole in an A4 sheet of paper with your hand?

The heading says it all, but let me explain it a little further. Suppose you hang a sheet of paper (A4 size) from one end leaving the other end free. Now practically it seems impossible to punch a ...
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1answer
49 views

Why friction force peak just before the object moving?

This diagram shows the amplitude of friction force of a typical contact-surface object. The friction force increases as we apply an internal force until it reach a maximum value just right before ...
0
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0answers
28 views

An elaborate pulley consists of four identical balls at the ends [closed]

I'm doing the problem $7$ from this book, but I can't understand the resolution, so I'm doing my own: Since the block will fall with speed $v$ for a distance $d$, the difference in potential energy ...
1
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2answers
105 views

How this formula for work follows from the definition?

If a particle moves along a path $\gamma : I\subset \mathbb{R}\to \mathbb{R}^3$ then the work done by a force $\mathbf{F}$ is defined by $$W = \int_{\gamma} \mathbf{F} = ...
0
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1answer
45 views

Moments and forces, when part of the scenario involves a circle or arc rather than a straight line

Some questions below, involving strategies, regarding the following problem: A hoop of weight $20$ Newtons can rotate freely about a pin fixed in a wall. A string has one end attached to a pin, ...
1
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1answer
103 views

What is the physics in a balero toy? [on hold]

A balero is a wooden ball tied with a string to a rod. The string ties to the ball at one end (say North pole), and there is a hole drilled in the ball at the other end (South pole). The hole is the ...
2
votes
2answers
60 views

Why don't both equivalent forms of this delta function give the correct answer?

I am a bit confused on a basic problem involving a Dirac delta function being integrated over in a multiple integral. The original problem is to find the probability distribution in position-momentum ...
1
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1answer
29 views

Terminal velocity of a raindrop

I have solved the question and got the answer , but I do not understand why will the raindrop attain a terminal velocity.Without any resistive forces why does it attain a terminal velocity?
3
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3answers
94 views

What is the time period of an oscillator with varying spring constant?

It is well known that the time period of a harmonic oscillator when mass $m$ and spring constant $k$ are constant is $T=2\pi\sqrt{m/k}$. However, I would be interested to know what the time period ...
10
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3answers
5k views

Can superconducting magnets fly (or repel the earth's core)?

If a superconducting magnet and appropriate power supply had just enough $I\cdot s$ (current $\cdot$ length) so that when it was perpendicular to the earth's magnetic field, the force of the ...
5
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7answers
3k views

Intuitively, how can the work done on an object be equal to zero?

To my understanding the work done on an object is defined mathematically as: $$W = \vec{F}\cdot\vec{S}=|\vec{F}||\vec{S}|cos\theta$$ This, I understand. My problem is that I don't understand that if ...
0
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1answer
46 views

Inverse square law in one dimension [closed]

A point of mass $m$ is at rest at position $b$ and subjected to a force $f(x) = -k x^2$. We are to show that the time required for the particle to reach the origin is $$ \pi \left( \frac{m b^3}{8 ...
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3answers
436 views

Why does the moment of force (aka. torque) depend on the perpendicular distance?

Couyld anyone explain how the lecturer concluded that $$(\underline{r_2} - \underline{r_1}) \times \underline{H} = \underline{p} \times \underline{H}$$
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3answers
73 views

How can Kinetic energy formula and the Work formula be derived without assuming the other to be true?

After searching how to derive the formula for Kinetic energy, I found that most derivations required the use of the "work" formula. After searching how to derive the work formula for a bit, I found ...
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2answers
37 views

Conditions for vertical circular motion

If a bob attached to a string is swinging in vertical circular motion, we say that the bob leaves the circular path when the tension in the string becomes zero, but even when tension becomes zero, ...