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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2answers
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Physical interpretation of Fourier $[x(t)]$ where $x(t)$ is the position of mass $m$ as a function of time?

If a macroscopic body of mass $m$ moves according to a certain law of motion like, for example, $$x(t)=A\cos(2\pi ft)$$ then what physical interpretation can be attributed to the Fourier transform of $...
4
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1answer
141 views

The Lagrangian of a Rocket

I am trying to understand how to write the Lagrangian of a system which consists of a rocket losing gas mass in a rate of $\frac{dm}{dt}$, the gas moving in a velocity of $u_0$ in the rocket's view? ...
2
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1answer
63 views

Universe Expansion - Could galaxies be moving away from each other due to photon bombardment?

We know galaxies are moving apart from each other due to the ability to look at the color shift of those galaxies. The fact that galaxies are moving apart seems to be most-widely attributed to the ...
0
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2answers
70 views

How do gravity anomalies on Earth comply with conservation of energy?

Gravitational acceleration varies from place to place on Earth in a range of about 0.02 percent and is caused by density distributions within the Earth. Imagine an experiment where you move around the ...
2
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1answer
76 views

Does third law of motion apply to light or EM waves? [duplicate]

Third law of motion - "For every action there is an equal and opposite reaction" I was considering the situation, where I may be motionless in space with only a flashlight and no forces acting on me. ...
2
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1answer
103 views

Perturbation Method in Mechanics: Average velocity of a small mass on a vibrating inclined plane [closed]

I've stumbled across this delightful and difficult collection of problems, by Jaan Kalda. The following problem has stumped me. (It's probem 16 on the sheet, which I have provided as a link) http://...
0
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3answers
161 views

Does the work done by a person equal the work done on the object in this situation?

If you applied a constant force over a floor that has friction on an object, would the work done by the person equal to the work done on the object? Assume that the floor is flat and that the object ...
23
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4answers
6k views

Why doesn't a spinning object in the air fall?

Let's say I have a ball attached to a string and I'm spinning it above my head. If it's going fast enough, it doesn't fall. I know there's centripetal acceleration that's causing the ball to stay in a ...
1
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0answers
43 views

What does the Scattering Amplitudes tell us about the interactions of matter

I am confused as to the role of the wave function in quantum mechanics. My understanding is that the wave function/state vector is purely a algorithm or mathematical means to compute the results of ...
1
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2answers
49 views

Does air resistance give a falling skydiver weight?

An observer in free fall is weightless as he is accelerating at 9.8 m/s^2. However, when a skydiver jumps from a high plane, his acceleration gradually slows until becoming 0 m/s^2 at terminal ...
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2answers
33 views

Kinetic Energy and a force [closed]

An object is moving at a constant velocity mass $m = 5 kg$ velocity $v = 20m/s$ Kinetic energy $K = 1000 joules$ If I divide $K$ by the distance traveled in 1sec I get a force $f=50N$ What is ...
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1answer
71 views

Properly deriving the formula for the kinetic energy

I am a physics student and recently attended my first lectures. One thing that strikes me even now was the way the professor derived the formula for the kinetic energy. He started with the (already ...
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1answer
65 views

Zero Energy State of a Mechanical System? [closed]

Would a mechanical system in a particular frame (when I say mechanical I mean pulleys, elastic strings, etc.) that has no potential energy (loaded springs, pulled back elastic, hanging weights, etc.) ...
0
votes
3answers
102 views

What's the work done by a spring on a block when it moves from extreme to mean position?

I really don't know where am I doing it wrong, but block when it moves towards mean position displacement will be along the force right, so the force acting on block will be $+fxdx$ Integrating we ...
0
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2answers
43 views

Phsyics Energy Problem + Concept

A simple problem really. Part 1 Suppose a ball ($20. ~kg$) was shot straight up with an initial velocity of $+50~m/s$. a. Assuming that all of the ball's initial $E_k$ was transformed into $...
0
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1answer
325 views

When dealing with pulleys and hanging masses, does one add or subtract tensions to find torque?

I'm very confused on this problem. A pulley has two hanging blocks on either side with one having a greater mass. To find the torque, do I have to add the tensions of both the blocks or subtract the ...
0
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3answers
49 views

Do I need to have a force acting in an opposite direction to feel the force of acceleration?

Suppose I'm in a rocket, accelerating away from the Earth. While I'm accelerating away from the Earth in the rocket, I can feel the force of acceleration. Now, let's suppose we take away the Earth, ...
2
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0answers
73 views

Precession of angular momentum vector

I'm studying Classical Mechanics on Goldstein's book, so I'm using his terminology and notation. First I'll explain where the question comes from: consider a heavy symmetrical top and consider the ...
2
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2answers
140 views

Why Earth is considered to be an inertial frame? [duplicate]

Earth rotates about its axis and also revolves around the Sun at the same time. So why Earth is considered as an inertial frame in Newtonian Physics. So technically, I'm effectively asking why the ...
0
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1answer
89 views

Newton Mechanics [closed]

I am confused about this question, what does it mean? A particle has a mass of $2\ \mathrm{kg}$ and a force $$F = 24t^2 i + ( 36t - 6 ) j - 12tk$$ acting on it. At the time $t = 0$ the particle is at ...
0
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2answers
101 views

Does friction depend on the direction of motion?

In my experiment of finding the moment of inertia of a flywheel, I first rotate the flywheel in the anticlockwise direction and then in the clockwise direction, but I am getting different values of ...
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0answers
18 views

Can we use the planets and Sun to fling out a craft at relativistic speeds? [duplicate]

E.g. The Voyager crafts took various assists from the planets. Sun being much more massive, wouldn't a spacecraft gain much more energy from such a flyby on the correct trajectory? If so then what ...
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1answer
43 views

Impact on landing with forward motion vs straight down

A skateboarder ollies down a set of stair. Is the impact when landing less than if dropped straight down from the same height?
3
votes
5answers
877 views

Why can't I push myself in a chair? [duplicate]

If I am sitting in a chair with wheels and someone pushes on the back of my chair with sufficient force it will role along the ground. However, if I push on the back of the chair with the same force ...
0
votes
4answers
189 views

Force exerted on carseats?

Can anyone explain how force is exerted on car seats during a crash? I am being told in car seat safety forums that $force=mass \times acceleration$. So if a $2000 \;\text{lb}$ vehicle bumps you at ...
0
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5answers
169 views

What is the proper vector form for the Gravity Formula?

We are familiar with the equation for calculating the velocity of an object in orbit given the central mass (or the mass given the orbital velocity): $$\frac{v^2}{r} = \frac{MG}{r^2}$$ I'm trying to ...
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0answers
16 views

Are the effects of faraday's law of induction worth considering in this experiment?

In my intro to physics lab at uni, we did an experiment where we were supposed to measure the amount of kinetic energy and momentum before and after collisions between two carts. For some reason, ...
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2answers
142 views

How to start an artificial gravity?

I understand how artificial gravity in space stations works. It is by normal force the wall exerts on the foot. But I wonder how to start it in the first place. I just learned about centrifugation ...
0
votes
1answer
32 views

If there is a non-slipping string pulling a cylindrical object, is the rotational acceleration the same as the translational acceleration?

The rotational velocity and translational velocity are the same right? Assuming the cylindrical object does not interact with anything other than the string which applies a force.
0
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0answers
776 views

Inertia of yo-yo goes to infinity, what is tension and acceleration?

For this part, imagine that the string is wound around the center axle of a yo-yo; the axle radius is Raxle, but the yo-yo casing has a radius Rcasing≫Raxle and moment of inertia I≫mr2axle. In the ...
3
votes
0answers
115 views

From Newton to Kepler without infinitesimals

I've read some interesting calculus-free proofs of at least parts of the derivation of Kepler's Laws from Newton's gravitational force. One is of course Feyman's "Lost Lecture" (which was already ...
0
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2answers
55 views

Finding the work done to fill the tank by pumping water over the edge? [closed]

I am really confused on how to approach the following question and how to set it up. So the question is: An open tank has the shape of a frustrum of a right circular cone. The tank is $4\:\mathrm{...
1
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2answers
91 views

How much fuel do I need to send cubesat 1kg from Earth orbit to Moon orbit? [closed]

How much fuel do I need to send cubesat 1kg from Earth orbit to Moon orbit? And how much stages? For i.e. C12H22O11 + KNO3, polyethylene + oxygen or kerosene + oxygen.
0
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1answer
208 views

Why are inclined push-ups harder?

I came up with a random question which looked simple, but I can't work out the answer. The question is, why are inclined push-ups harder? And by inclined push-ups I mean push-ups with your legs on a ...
1
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2answers
113 views

The acceleration of the centre of mass [closed]

Given two balls that are thrown straight up in the air at a speed of $40 \:\mathrm{m/s}$, $0.10 \:\mathrm{s}$ apart. One ball is twice the mass of the other. The heavier ball is thrown second. I'm ...
1
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1answer
114 views

Spring-mass system with complex spring constant

Suppose a system containing a mass $m$ on frictionless surface, attached by a spring to a wall. The spring's constant is complex, given by $K = K_1 + K_2i$, with $K_1 \gg K_2$. Write the equation of ...
2
votes
1answer
37 views

Acceleration in an elliptical binary system

So I'm having a bit of a problem dealing with binary systems. I'm looking at acceleration in a stellar system and am not sure where to begin. Assuming both stars are of equal masses, they'd be equal-...
0
votes
1answer
204 views

Finding a Differential equation for falling chain

This is a chain wound loosely to a peg at the edge of a high platform. It has a total length of $L$ in feet and is hanging initially $x_{0}$ from the platform plus it's weight is $w\:\mathrm{lb/ft}$ ...
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0answers
29 views

Force and inclined plane

An incline of mass $m_2$ can move without friction on a horizontal plane. A block of mass $m_1$ is fixed to the incline with a piece of string. How does the system move when the string is burnt? The ...
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3answers
136 views

What happens if a machine controlled by me from Earth strikes the Earth? [closed]

SITUATION: Suppose I am a mad scientist and I have made a machine which has enough mass to push the earth. Now I am controlling the machine with a remote control with which I can change its speed, ...
-1
votes
2answers
59 views

Why is only one end at rest when a rope is attached to a cube? [duplicate]

I know there is something wrong in the way I think about physics generally, but I don't know what it is. Suppose there is a cube with a hook on one face and a rope attached to that hook (see diagram)....
0
votes
2answers
120 views

Conservation of momentum when a shell is fired from a cannon

When a shell is fired from a cannon free to move on a horizontal surface and inclined at an angle say 45 degree with horizontal. Does relative velocity of shell with respect to cannon depends on ...
2
votes
1answer
73 views

If the Moon had a large piece blown out would it remain tidally locked?

I just saw this video on Sonic Adventure 2 trivia where it's mentioned that part of the Moon was blown up but in later games it's whole. It was explained away as the Moon simply rotating to show the ...
1
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1answer
59 views

When does an object rotates and translate at the same time?

I have a ruler on the table. If I push it with my finger on its end, it will rotate. but if I push it hard enough, it will rotate and slide slightly. Which force cause this sliding motion? and how ...
15
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7answers
3k views

What does an undefined formula in physics mean?

I am trying to figure out how undefined formulas in mathematics relates to physics. Take the following formula for terminal velocity. $$V_\text{terminal} = \sqrt{ mg \over{c \rho A}} $$ Say we have ...
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1answer
50 views

Alternative method for pulley system not working

We have two a pulley system with two masses of 2kg and 3kg on two ends of a massless string. At the end of 5 seconds, the string breaks. How far up did the 2kg block move? Here's what I have tried:- $...
1
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1answer
34 views

Phase space orbit for a projectile [closed]

After playing around with drawing the phase space orbit for a harmonic oscillator I started wondering about the case for a free falling object. So the equations of motion are: $$ P = P_0 + mgt $$ ...
3
votes
1answer
130 views

Orbital equations of motion with respect to energy

Consider the equations of motion of an object in an orbit around a central body. We use an inertial frame originating at centre of mass of the central body: $$ \frac{d\mathbf{r}}{dt} = \mathbf{V} \tag{...
1
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1answer
91 views

How to conserve angular momentum?

If i want to conserve angular momentum from the point of contact of the solid sphere and the ground how should I do it? I know we can use $mvh = I\omega + MvR$ ,if the collision is elastic. But in ...
1
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0answers
77 views

Uranus, the Physical model to change it's rotation axle

Uranus rotates pretty wierd, it's 90-degrees tilted; Why is Uranus's axis of rotation tilted? The best answer for this is; that at a distant point in its past, Uranus was struck by a very ...