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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Time spent in eclipse of an object

Well consider an orbit - I'm trying to calculate the exact time spent in the shadow of the body you orbit around. An explanation of "shadow" (sun is positioned to the far left): For a circular ...
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Why do objects move when you apply a force that's equal in magnitude to the friction? [duplicate]

If the friction on an object is 200 N and you apply 200 N, it seems, the forces should immediately cancel each other out since the friction and your applied force go in opposite directions, leaving ...
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Why is friction not dissipative in rolling motion? [duplicate]

We know that non-conservative forces like friction is a dissipative force. But according to my book when a solid cylinder is rolling down a rough inclined plane of inclination angle $\theta$ the ...
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What is the distance between two objects in space as a function of time, considering only the force of gravity? [duplicate]

What is the distance between two objects in space as a function of time, considering only the force of gravity? To be specific, there are no other objects to be considered and the objects in question ...
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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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Pushing down on the gas pedal of a car a good example of jerk?

I'm trying to think of the clearest examples to demonstrate the concept of jerk to a layman. Ignoring drag and making other reasonable assumptions (friction is conveniently there to only allow you to ...
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Conservation of momentum in inelastic conservation

Why does momentum and velocity change along contact normal but not contact tangent In in elastic collision? Suppose a ball strike an inelastic surface. It's velocity component does not change along ...
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Roller Coaster Physics

I am trying to figure out how to calculate the $g$-forces throughout a non-uniform corkscrew as well as the exiting velocity. Do you calculate each radius separately and each $g$-force separately ...
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Defining gravitational potential

I recently came across the definition of gravitational potential where ..... Suppose a particle of mass $m$ is taken from a point $A$ to $B$. Let $U(A)$ and $U(B)$ denote the gravitational ...
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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? ...
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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 ...
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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 ...
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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. ...
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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://...
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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 ...
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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 ...
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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 ...
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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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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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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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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.) ...
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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 ...
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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 \$...
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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 ...