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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In the following problem, where did $v_{cm}$ come from? [closed]

In the following problem, where did come from? I don't recall any formula that this equation could be derived from...?
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170 views

How can one conclude upward force is related to tension in this question?

In preparation for the SAT Physics Subject Test, I have been doing extra practice problems. This one states: A garment bag hangs from a clothesline. The tension in the clothesline is $10 \,\text{N}$ ...
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4answers
328 views

Why don't hexapods gallop?

I haven't observed any terrestrial hexapods that gallop like agile tetrapods(cheetahs/horses). Instead, I've observed that all of them scuttle which constrains their maximum velocity. And after ...
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Riemann Invariants

I understand that the Riemann Invariants for an expansion wave (isentropic) are constant along the particular characteristic line i.e.: $u + \frac{2c}{\gamma-1} = const $ along $dx/dt=u+a$ (1) ...
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7answers
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Why don't we feel the subtle speed change of Earth's elliptical orbit?

Earth's orbit is a slight ellipse, so to conserve momentum its speed increases when it is closest to the Sun. If the speed changes there is an acceleration. If there is an acceleration there is a ...
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2answers
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Setting up equations for a vertical spring-mass system [closed]

I am preparing for an exam in classical mechanics and today I have encountered a slight problem when solving a more complex spring-mass system. Consider the following setup: Then the system of ...
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0answers
30 views

Moment of Inertia of a curved part of a graph [closed]

How to find the moment of inertia of a curve about a given axis. For example : How can we find the MI of the curved part of :$$\sin x\ $$ EDIT: Assume the range from $$[0 ,2\pi ]$$ and the axis to ...
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2answers
228 views

Breaking Newton's 3rd Law?

I am having trouble explaining how the following experiment actually works, but it does.? Place a neodymium magnet on a piece of Styrofoam and a test tube of water next to it on the same piece of ...
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0answers
45 views

Please tell me which of the Equation is wrong; the Angular momentum or the momentum? [closed]

(Sorry, it's not 2M. It's m+M) Two rigid body is fastened at a stick. A bullet collides into the first body and become one, and the stick rotates. When the bullet collides, there is no outer torque ...
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2answers
80 views

Why does Goldstein's derivation of orbits from Newton's law not yield the orbit consisting of symmetric oscillation along a line thru center of Sun?

Why does Goldstein's derivation of Keplerian orbits from Newton's law of gravity not yield the orbit consisting of symmetric oscillation along a line passing thru the center of the Sun? The fact that ...
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0answers
90 views

Foucault pendulum, where did I go wrong?

I wanted to approximate the number $N$ of periodes needed, such that the foucault pendelum turns one time. Though my result is off by the factor 2 of the results I found. What I did: I assume the ...
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2answers
146 views

Kepler Orbits: Small Perturbations->Elliptical Orbits

A group of my physics classmates and I have been stuck on this problem. We have tried a few approaches. The problem is to show that a body following a circular orbit, when given a small radial ...
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0answers
37 views

All about Frictions. (Help me) [closed]

A 20-kg body is on a plane inclined at 60° from the horizontal. The coefficient of friction is 0.22. What force at 30° with the plane will cause the body to move upward at a uniform speed? 2.A block ...
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3answers
2k views

Why is the period of rotation the same for two stars orbiting the same centre?

In a binary star system, two stars $A$ and $B$ follow circular orbits, of radius $R$ and $r$ respectively, centred on their common centre of mass $O$. The mass of star $A$ is $M$, and that of star $B$ ...
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3answers
110 views

Why centripetal force does not increase the value of tangential velocity? [on hold]

I found in a text book that the value does not change because the centripetal force is perpendicular to the tangential velocity. But I am confused, because a vector can have a component, which is ...
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1answer
53 views

Can an object take off from A, do not move (in the air) but land at a different place? [closed]

Can an object take off at a point A on the surface of the Earth and then land after some time only to land at a different place where it initially took off (because in the mean time the Earth has ...
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0answers
12 views

Newton's law - satellite position (in 2D) for specific moment of time [closed]

I’m trying designate function that calculate satellite position (2 dimensional) for specific moment of time for better understanding Newton's law of gravity. To verify my calculations I created second ...
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0answers
33 views

Dynamics of pendulum coupled to a gyroscope [closed]

We know the dynamics of a pendulum and we know the dynamics of a gyroscope. I put together the following I diagram below. The interesting thing as that the system has a beat frequency where the ...
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1answer
28 views

Conservation of Energy with Rotation Caused by Friction

A book that I am using to study poses the following problem: Suppose you wish to use a spring with a force constant $k$ to launch a spherical ball or radius $r$ and mass $m$ up a ramp of inclination ...
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1answer
85 views

Validity of Point Mass Approximation in Newton's Laws of Motion

Chapter 2 of Kleppner & Kolenkow's An Introduction to Mechanics reads as follows - Newton's Laws describe the behavior of point masses. In the case where the size of the body is small ...
6
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4answers
140 views

Will a tennis ball go further if i hit it with the side of the racket?

If i hit a tennis ball 'properly' on the stringing, does it go further than if i rotate the racket 90 degrees in my hand and hit the ball with the same force, but on the side of the frame? I'm ...
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1answer
57 views

Why does galilean invariance imply that particles that start rest stay on the same line?

I'm reading Arnol'd for self study. I'm struggling with this question: "Show that any system of two particles will remain on the same line that connected them at the initial moment, if they started at ...
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0answers
44 views

How to calculate the time for reaching 1/2 of the height for an object [closed]

I need to calculate the time for reaching the red object to the 1/2 of it's height. Can somebody provide me some guidelines?
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1answer
104 views

Calculate torque to rotate and 84lb panel vertically from 0 - 90 degrees

I have a rectangular panel that weighs 84lb. Width (rotational axis) is about 60-inches. Height is about 32 inches. It will be lying flat and hinged (or connected to tubular motor) on the long edge. ...
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1answer
52 views

How would you go about solving this difficult physics problem? [closed]

I was able to calculate an angular frequency of 85.4357 rad/s for this mass. However, I am confused as to what to do next. Any ideas?
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1answer
187 views

Cause of SHM of liquid-column in V-tube

Suppose there is a v-shaped tube filled with water. The left limb is at $\theta_1$ & the right limb is at $\theta_2$ with the horizontal base. Initially, the level of water in both the columns are ...
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2answers
180 views

Effect of position on a motorbike turning

While searching tips for driving a motorbike on wet roads safely, I heard some pilots saying to lean inside the slope makes the bike less tilted, so it's safer. I agree leaning make the bike less ...
3
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2answers
58 views

How do I calculate a upward-pulling force on a swinging pendulum?

I'm trying to implement a simple pendulum using a 2d physics system that can model rigid bodies with gravity. The problem is that I don't know how to calculate the upward-pulling force of the rope, as ...
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5answers
382 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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2answers
43 views

Why is $mg$ positive and $N$ negative in this problem?

In this problem: A car of mass $430\ \mathrm{kg}$ travels around a flat, circular race track of radius $178\ \mathrm{m}$. The coefficient of static friction between the wheels and the track is $0....
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2answers
99 views

Why do Newton's laws hold in a normal and tangential coordinate system?

In my book it says: When applying the equations of motions, it is important that the acceleration of a particle be measured with respect to a reference frame that is either fixed or translates ...
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1answer
50 views

Photon absorbsion through 'quantum foam' [closed]

Over the cosmological distances that the photons travel from distant sources, will 'quantum foam' have an effect on them before they reach us? *Re NASA Science News Dec 31st 2015. The effect on ...
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3answers
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Where does the force to stop a constant velocity object come from?

If a ball hits a wall at a constant velocity, it will slow down and eventually come to rest. Since the ball was at constant velocity, it was not accelerating, and so there was no force. Also, the ...
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1answer
75 views

Is it possible to throw a stick without giving it a rotational motion?

When walking with our dog I always throw wooden sticks for her. Then one time I wondered if I could throw the stick (normaly, so not like a spear) without imparting on it a rotational motion around ...
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0answers
34 views

Why does the amplitude of the pulse never return to its original value when the number of waves used to construct it tends to infinity?

I was reading Constructing a pulse of Modulations, Pulses, and Wave Packets from Waves by Frank S. Crawford Jr. ; here, in the following concerned excerpt, the author is describing of constructing a ...
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0answers
42 views

Formula for altitude of an accelerating rocket [closed]

I'm trying to find a formula for a rocket's altitude including the change in the rockets mass due to fuel being consumed. The normal formula I would use would be $\mathrm{ (Thrust/Mass )} \cdot 9.81x^...
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0answers
16 views

Find the mass of Europa, one of the Moons orbiting the Jupiter [closed]

Europa, one of the moons of Jupiter, was discovered by Galileo in $1610$. Europa has a circular orbit of radius $6.708\times 10^5$ km and period $3.551$ days. Find the mass of Jupiter. My attempt: ...
2
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1answer
867 views

Relative wind velocity explanation - understanding Irodov problem 1.6

I am having trouble understanding the reasoning behind the solution in this Irodov General Physics problem. The problem is 1.6: 1.6. A ship moves along the equator to the east with velocity vo = ...
0
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1answer
28 views

Does a counterweight eliminate recoil/counter-torque?

A long, long time ago, I remember reading some scifi book that involved catapults whose throwing arm had a counterweight at the other end, such that the arm was balanced. The counterweight was not ...
3
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5answers
164 views

A question on uniform circular motion and minimum tangential velocity

I've had a bit of a crisis in my understanding of circular motion and I'm hoping to clear it up here. Would it be correct to say that the condition for a particle to be in uniform circular motion is ...
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2answers
31 views

Pressure in deodorant can

Pressure in a deodorant can is greater than the surrounding pressure but still the can is in equilibrium with the surrounding . Why does this happen. If we apply $F = PA$ then $P_{in}A= P_{atm}A$ and ...
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0answers
52 views

Pulling and pushing two objects through a rigid member in between the objects [closed]

Problem statement: I have two objects of mass $m$ placed at some distance and connected each other in-between with a rigid member which can take compression or tension. Through a point on rigid member ...
1
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1answer
230 views

Why golf balls travel faster if they spin?

From the book I have been given to read I found that balls spin due to the centripetal force but i am confused about how exactly do the resultant force causes it to spin and move forward about the ...
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2answers
65 views

Frictional force on an inclined plane with applied force = Mgsinx - Mgcos x?

I was reading Introduction to Classical Mechanics (Morin) recently and came across this example, which said that the friction force (marked $F_f$) is $Mg\sin\theta - Mg\cos\theta$. However, I can't ...
4
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2answers
273 views

I know that free fall in vacuum is independent of mass. But what happens in air?

Pardon me if this sound somewhat trivial to some of the highly qualified users here. So I know two objects will fall at the same rate if they are in absolute vacuum, so what I'm assuming is that the ...
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0answers
145 views

Position vs Time Function for a Falling Object Without Assumption of Constant Acceleration [duplicate]

If you have an asteroid for example and a planet, isolated from all other gravitational influence and initially at rest with respect to each other, how would you find a position vs time function for ...
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2answers
82 views

Proving that force satisfies the laws of vector addition [duplicate]

A vector quantity has both magnitude and direction. So, for any physical quantity to be a vector, it should have a direction and a magnitude. Though this is a necessary condition for any quantity to ...
0
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0answers
12 views

Elastic Surface Waves

In the book by Landau and Lifshitz on elasticity they introduce the concept of surface waves. Does anyone know how to write down a Lagrangian including source terms for surface waves? In this case, a ...