# Tagged Questions

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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### Newton's third law at the quantum level? [closed]

let's look at force at the atomic level to understand the newtons third law of motion. I'll use Helium atoms as an example. Now imagine we start with one atom HE2 stationary, and throw another atom ...
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### Prove that time for planet to fall into the Sun equals $\left( \frac { 1 }{ 4\sqrt { 2 } } \right)$ of the planet's period [closed]

If a planet was suddenly stopped in its orbit supposed to be circular, show that it would fall onto the sun in a time $\left( \frac { 1 }{ 4\sqrt { 2 } } \right)$ times its time period. I am ...
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### Forces acting on a jet pilot [closed]

I found the forces at A and C with no problem, when it came to the forces at B I found the normal force of the seat on the pilot but the forces in the tangential direction got me. The solutions ...
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### Understanding transverse oscillation in 1 mass, 2 spring systems

Lately I have been working through some nice problems on mass-spring systems. There are tons of different configurations - multiple masses, multiple springs, parallel/series, etc. A few possible ...
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### Second Kepler's law implies that constant velocity

I was trying deduce that if we suppose that the planet's orbits are circular and de Kepler's secong law is true: A line joining a planet and the Sun sweeps out equal areas during equal intervals of ...
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### Ball Bounce Acceleration at the Point of Bounce [closed]

simple question but I wanted to confirm my approach of thinking about the problem. Question: A rubber ball is dropped from the fifth story of a building and free falls to the ground, after which ...
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### How a wheel move on the earth?

I was wondering how a wheel move on the earth ,I mean if friction causes it moves so what causes it stops after a while without any pushing force? I think that the direction of the friction force is ...
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### Why doesn't the 9th ball move in the break in the nine-ball pool game?

In the game of nine-ball pool, we break the rack like shown below: In the break, we hit the 1st ball with the cue ball. Many people familiar with pool games say that if the rack is constructed ...
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### Frames of reference, energy and different observations (non-relativistic)

I have had trouble reconciling the quadratic form of kinetic energy and reference frames traveling at different velocities for some times now. I'll give an example that confuses me for some ...
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### Why do icebergs move perpendicular to the wind?

I know it has to do with to Coriolis force and the Ekman layer but I didn't really understand the explanation. From Wikipedia: "Ekman transport, part of Ekman motion theory first investigated in ...
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### Mechanical energy of a body

What is the total mechanical energy of an air-plane flying in the sky? Does it possess both kinetic energy and potential energy,taking the zero potential energy at ground? As it is moving it will ...
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### Confusion with Newton’s third law

Suppose i push a box with my hand which has a mass=1kg. I apply a force of 2 newtons and it will accelerate at 2m/s^2. But, according to the third law, the box applies a force on me, which is also ...
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### How many legs (minimum) would a chair need in 4 spatial dimensions for you not to fall?

I was reading another post in physics.SE about chairs when this question arose. My guess is we would need more than in 3 dimensions as in 2 dimensions you would just need 2 (I think). I've been trying ...
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### How can one prove mathematically using a thought experiment that a simple pendulum will vibrate forever in an ideal condition (no friction) [duplicate]

Let's say I have a simple vibrating pendulum, if there is no friction in the space, will it vibrate forever or will it stop? How can one prove this mathematically? I tried but failed, can somebody ...
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### Which system's mechanical energy is conserved?

As the figure shows, $m$ starts falling down from its current position at the original speed of zero. And $M$ is a curved side trapezoid. All friction can be ignored. |# <- This hash stands for ...
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### How am I able to stand up and walk down the aisle of a flying passenger jet?

The energy of a moving object is $E = mv^2\;.$ That is it increases with velocity squared. I walk at say 3 miles per hour, or lets round that down to 1 meter per second for a slow walk. I weigh less ...
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### Two trains collision problem [closed]

Consider two trains $A$ and $B$ travelling on a line one towards the other at speed $v_A=v_B=90km/h=25m/s$. When they are $511m$ apart the driver $A$ start braking with deceleration ...
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### Confusion regarding the forces in a system of particles

I think the internal forces in a system of particles is zero. But is it possible for the sum of internal forces to be non zero in any case?
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### Two mass spring system

The equations of motion of the spring mass system with, m = 1 $\ddot{y_1} = -k_1y_1 + k_1(y_2-y_1)$ $\ddot{y_2} = -k(y_2-y_1) - ky_2$ My question is with the second term in the first equation. ...
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### Not sure how to solve a problem from online course [closed]

I'm not sure how to approach this problem. I don't know the magnitude of F1 or F2 and I'm not sure how to get it from F. Any help would be appreciated.
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### Bicycle counter-intuitive: in which direction it will move? [duplicate]

I saw this puzzle in a local newspaper: Consider a normal bicycle set to stand in its upright position, and its pedal is set to the position as shown in this figure. One man slightly hold the ...
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### Methods to use in problems with equations of motion, where is required to determine a particular acceleration

I've a doubt on problems with manipulation of equations of motion. I'll make an example of a situation I'm confused about. Let $A$ and $B$ be two points that move on a line with constant speed, ...
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### What powers a comet? [closed]

I know that a comet is a ball of ice, and I have tried the NASA page. http://spaceplace.nasa.gov/dr-marc-solar-system/en/#/review/dr-marc-solar-system/comet-power.html but they swerve around the ...
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### Effect of air resistance on maximum height of thrown stone

Suppose a stone is thrown upwards from the surface of the Earth in a (very large) vacuum chamber and reaches a maximum height of 1km. If the same stone is thrown upwards at the same velocity outside ...
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### Growth time of static friction

I have a doubt about the best model of friction to use ina dynamic simulation. The most popular model, the Coulomb-Morin's friction, is defined by: $F =\cases{ -F_d \cdot sign(v) & with$v \neq ...
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### Motion of $n$ bodies connected with springs

Let's consider $n$ cuboids moving without friction, each of mass $m_i$. Each wo neighboring cuboids are connected with a spring of the coefficient $k$. ...
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### Why do the stars in a binary system, revolve diametrically opposite to each other?

I encountered this question, as I was reading up on Gravity. The author of my textbook says that the stars orbit a common centre which is their center of mass. I somehow think that this fact might ...
Suppose a ring is rotating in space with an angular velocity $\omega .$ Then each element of the ring is having an acceleration of $m\omega^2 r$ ($r$ is the radius of the ring) but what force is ...