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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98 views

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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32 views

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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55 views

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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1answer
61 views

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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30 views

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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1answer
30 views

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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1answer
84 views

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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2answers
74 views

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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0answers
56 views

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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0answers
24 views

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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2answers
51 views

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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238 views

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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0answers
29 views

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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3answers
57 views

How to apply a force vector to a position vector?

A particle is present in the two dimensional space. It's position is given by the vector: $$x = \begin{pmatrix} |x| \cos(\theta) \\ |x| \sin(\theta) \end{pmatrix}$$ It experiences a force of: $$ F = ...
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1answer
55 views

Seesaw Physics - Shipping Container House Problem

I'm currently building a house using shipping containers. One of the containers is in a cantilever position, sticking out from the base concrete structure like this: ...
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1answer
60 views

A projectile is shot straight up from (non-rotating) Earth's surface at a speed of 10,000 km/h. How “high” does it go (to 2 s.f, in m)? [closed]

What is wrong with my work? It continuously gives me an incorrect error, but I can't identify the step at which I made a mistake. My work is shown as follows: let the height be h radius of earth , r ...
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2answers
38 views

Terminal velocity of mentos [closed]

If somebody throws a mentos downwards (vertically) faster than the terminal velocity of a mentos, from the height at which the terminal velocity is reached from a falling mentos, will the mentos hit ...
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1answer
32 views

Finding acceleration in a pulley system

In the above system, mass A is accelerating at $a$ upwards. The question then asks to find the magnitude of mass B's acceleration, in terms of $a$. I know that throughout the massless string, the ...
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0answers
26 views

Newton's mechanics. Axioms, postulates, etc

I am trying to write all the assumptions or postulates to set up Newton's mechanics: 1.- The space is infinite, continuous, homogeneous, isotropic and 3-dimensional. By this way, we assume that the ...
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1answer
11 views

Center of Instantaneous velocity in two degree of freedom problem

I have a problem like this I have two DoF where the force F is acting on the car and another force could be acting on the coordinate $q_1$. The force acting on $q_2$, the coordinate of the car will ...
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0answers
54 views

A box half filled with water is given vertical and horizontal acceleration [closed]

Question: A box of of height 2m, width 6m and length 6m is half filled with water. Then it is given a horizontal acceleration of $\frac{g}{2}$ and vertical accleration of $\frac{g}{2}$. Find the angle ...
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2answers
72 views

Will I die from a 50-foot fall? [closed]

Sorry if I didn't ask this in the right place, but... Will I die from a 50-foot fall? What are the chances of survival? I know this is more of a biology question or something, sorry :(
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1answer
27 views

Relative velocity

Question is from Barron's SAT subject test Physics "A flat railroad car is moving to the right at 5m/s. A person standing on the car throws a ball straight upward at 20m/s. If air resistance is ...
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1answer
18 views

determine force from a hammer to pull out a nail

Hi the force from the hammer is 5,4 * F according to my book .. How did they calculate that ? Should not it be 27 * F thanks
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1answer
33 views

first and second moments of mass

why is the second moment of mass used as moment of inertia, and why is the first moment of mass about an axis not used as moment of inertia? i understand that first moment is product of mass and its ...
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11answers
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Why are four-legged chairs so common?

Four-legged chairs are by far the most common form of chair. However, only three legs are necessary to maintain stability whilst sitting on the chair. If the chair were to tilt, then with both a ...
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2answers
35 views

Force applied by a spring stretched to a different direction

This may be a bit basic but I am unsure of the answer. Assume the following simple setup: a spring with a spring constant k and of length L, connected to mass m. What is the force applied by the ...
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1answer
97 views

Is it possible to pull a car at a constant speed?

Suppose we use a trailer to pull a car, which has a damaged motor. The car moves at a constant speed, assume that air drag is negligible and the wheel does not slide on the road, it only rotates. ...
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2answers
41 views

Why does an ice hockey stick, when thrown on ice always rotate and translate together before coming to rest? Why not only rotate or only translate?

When a hockey stick is thrown on ice it simultaneously rotates and translates before stopping. Friction probably plays the main role here, along with the shape of the stick. I think maybe it is due to ...
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0answers
57 views

A leaf-cutter ant can lift 50 times its own weight. Can a human-sized ant lift a baby blue whale? [closed]

I found this statement/fun game in a nearby insect zoo: It says that as leaf cutter ant can lift 50 times its own weight, if you're 120 pounds and as strong as an ant, you could lift a baby blue ...
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1answer
66 views

Why Poisson's equation is important?

The Poisson equation can be deduced by Newton's mechanics: $$\Delta \Phi =-4\pi G\sigma$$ Einstein tried to give a "Poisson's equation" that works with his theory. This equation seems to be ...
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1answer
53 views

Equivalence between principle of least action and minimum potential energy

Are the principle of least action and the principle of minimum potential energy equivalent? How does one show that? Also, are Newton's laws of motion equivalent to the principle of least action? How ...
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3answers
54 views

Is mass directly or inversely proportional to time? [closed]

From a Newtonian perspective: F = ma F dx = ma dx E = m (dv/dt) dx m = (E dt) / (dv dx) Mass is directly proportional to time, if time slows down then mass goes down or decreases. From a ...
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1answer
98 views
+50

Relation between eccentric and true anomalies

If $v$ is the true anomaly and $E$ the eccentric anomaly, how can I show that $$\frac{dv}{dE}=\frac{b}{r}=\frac{\sin v}{\sin E}~?$$
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1answer
59 views

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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0answers
66 views

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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4answers
36 views

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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1answer
48 views

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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1answer
46 views

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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4answers
182 views

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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1answer
32 views

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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1answer
49 views

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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1answer
39 views

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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1answer
23 views

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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1answer
62 views

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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1answer
54 views

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 ...
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2answers
38 views

Cause of centripetal acceleration in a ring

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 ...
1
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28 views

Why do very small balls attached to a tiny spring propel themselves in hardly moving fluids? [duplicate]

I recall watching a youtube video about a ball with a spring on the idea propelling themselves through stable fluids without any assistance, even if we make sure the spring isn't moving in the ...