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Questions tagged [newtonian-mechanics]

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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Why coordinate axes are perpendicular to each other?

Coordinate axes are chosen to be perpendicular to each other because it is convenient, calculations are easier. This is what I have read. But in case that coordinate axes are per example 60 degrees ...
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2answers
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Which forces violate Newton's third law of motion? [on hold]

Forces arising from magnetic fields do violate Newton's third law of motion under certain circumstances. What other forces violate the third law?
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1answer
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Why does mass cause resistance to acceleration?

If I were in a vacuum with no gravity or friction, why would it be harder to push a floating bowling ball than a marble? Is there anything happening on an subatomic level that makes matter act ...
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Q: Inelastic collision homework [on hold]

Here's the original question: Two cars travelling in opposite directions at 36 m/s collide head-on and lock together. One car has the mass of 1000 kg; other has a mass of 800 kg. What is the speed ...
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1answer
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Can Momentum of an object change without net acceleration on the object? [on hold]

Comfy with single variable calculus and basic concepts of classical mechanics.
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1answer
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On the definition of Lagrange's equation

Is it really Newton's third law eq (1.5) ? Isn't the 2nd? I found it on "Abers Ernest Quantum mechanics".
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1answer
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Addition theorem for angular velocity --> “addition theorem for angles”

I'm wondering if it is possible to go from the addition theorem for angular velocity to the "addition theorem for angles". For example (I used the same notations of Wiki): $${^N\!\omega^B} = {^N\!\...
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2answers
48 views

Why can I not conserve kinetic energy in the following case? [on hold]

For the 2nd part of the question, if I conserve angular momentum about the centre of mass of the rod I get one value, and if I conserve kinetic energy of the rod and ball system before and after ...
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Normal Force on an object on the earth’s surface

If a body is on the earth’s surface at equilibrium, the forces acting on it are gravitational (by the earth’s centre) and normal (by the surface). These balance each other and allow the body to ...
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0answers
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Prove from first principles that a guitar string will vibrate at a constant frequency

From experience I am aware that a taught string will generally vibrate with a constant frequency. I wanted to prove this by considering the relation of distance from the resting position, and its ...
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2answers
2k views

What happens when the centripetal force is equal and opposite to the centrifugal force? [duplicate]

We say that centrifugal force is fictitious, yet we still use it in some problems. If the centrifugal force is equal and opposite to the centripetal force wouldn't that make the net force zero?
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1answer
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Why are angular velocity and angular frequency not measured in Hertz?

Recently, I was doing my homework and I found out that Angular Velocity and Angular Frequency can be calculated using $\omega=v/r$. This means the units of torque are (meter/second)/meter or 1/second. ...
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0answers
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How much more damage is caused after hitting a brick wall at 100mph over 50mph? [duplicate]

How much more damage is caused after hitting a wall at 100mph over 50mph? It is clear that there is just twice as much force generated after hitting a wall at 100mph, since the deacceleration is twice ...
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0answers
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Moving a (specific)-spacecraft without ejecting mass [on hold]

The idea is to move this spacecraft without ejecting any mass. The craft has two paddles which we can make spin. So we rev these two paddles up, spinning them in opposite directions and when their ...
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3answers
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Inertial and non-inertial reference frames

My book states that: A reference frame attached to earth is not inertial because it is revolving around the sun and it is rotating about its own axis. Don't we need a specified observer's frame ...
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2answers
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How propulsion in the “HELPING HAND” NetFlix episode works? *SPOILER*

I watched the "HELPING HAND" episode in NexFlix, and the protagonist is drift in space, every second she is more far from her ship, when her tank is out of oxygen, she throw her glove to make a ...
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0answers
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Fly wing velocity question [on hold]

A fly beats its wings at a frequency of 1200 Hz. if the expansion and contraction of the wing muscles of the fly exhibits simple harmonic motion, the angular displacement of each wing of the fly also ...
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0answers
24 views

Torque contacts

I experienced yesterday that when the slotted screw driver head was exact fit to the slotted screw, it was easier to turn the screw. I'd like to understand the physics of it. Is the bottom easier to ...
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0answers
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How does the momentum conservation law hold for gravitational interactions in special relativity with Newton's third law being invalid?

Griffiths' argument that Newton's third law is invalid in special relativity The selected answer to the post above talked about momentum conservation in electrodynamics – Newton's third law ...
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3answers
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Why doesn't a force perpendicular to the direction of motion change the speed?

It changes direction but not speed and this is proved in experiments. But is there any more "deep" reason as that space has isotropy and energy must be conserved per example?
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How to find Kinetic energy of the block of mass M?Please provide a detailed solution [on hold]

(https://i.stack.imgur.com/FcsvD.jpg)(https://i.stack.imgur.com/W0BE0.jpg) The spring of force constant k2 just touches the wall and is not attached to the wall.The natural lengths of the strings are ...
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1answer
62 views

What is my speed with respect to myself? [on hold]

Is it that my speed with respect me is always zero which means that throughout my whole life I am always at rest and the whole world is moving around me? I have another question: Suppose I am ...
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1answer
41 views

Two-body problem - point of closest approach

I am reading through an exercise : One of the hints to solve this problem is that at the point of closest approach the comet's velocity must be tangential only, why is this the case ?
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2answers
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Kinematics of particles

Do particles have to move in a straight line to apply Suvat equations? I always perceived that they do because acceleration can mean a change in the magnitude of velocity, a change in direction or a ...
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1answer
58 views

Difference between simple harmonic motion and angular SHM

I am not able to decipher when it is simple harmonic motion and when it is angular harmonic motion. Can we use both of them interchangeably? Can I know all the variable analogous for angular SHM (by ...
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0answers
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Manipulation with drag force [on hold]

I have a problem to solve concerning drag force and its relation with velocity. The problem is following: A car of mass m is propelled forward starting from rest by a constant force +F. Use b for the ...
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2answers
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Did Usain Bolt really sustain 11 horsepower of exerted power during the 100 m sprint?

I've just come across a WP article which says: "The Jamaican sprinter Usain Bolt produced a maximum of 3.5 hp (2.6 kW) 0.89 seconds into his 9.58 second 100-metre (109.4 yd) dash" Out of curiosity, I ...
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1answer
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Can this sum be done without integrating?

As by using conservation of mechanical energy, we can just be concerned about the final and initial position and the velocity could be found out. Am I not right? But I am not getting the correct ...
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0answers
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Is it possible relativity could have been discovered much earlier? [on hold]

Special relativity is a creation of Einstein. Mathematically unlike general relativity it is elementary. Is it conceivable Newton missed it? Or is it the case that it had to wait till the $20$th ...
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4answers
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Why doesn't a ball thrown upwards fall behind us if we're moving forward?

If we consider ourselves traveling in a bus and if we a throw a ball upwards, the ball should fall behind us according to law of inertia, right? If so why doesn't the ball always fall behind us each ...
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6answers
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Why is the total work done on an object its change in kinetic energy, but not change in total energy?

We have just started learning so explain simply. We don't know about conservative or non conservative forces. We are just learning basics.
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3answers
119 views

Why are large speaker cones required to to produce loud low frequency sounds?

Is there any reason for why a small speaker cone cannot produce low end sound at a comparable volume to higher frequencies? I can understand how a larger speaker would be in contact with more air and ...
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1answer
22 views

Oscillations - Mass Change on Simple Pendulum

The problem that I am thinking of is phrased as follows: A person on a swing is holding a sandbag and is moving with some initial velocity $v_0$ at the bottom of the swing of length $l$. The ...
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1answer
48 views

What would you call shelves failing after being bumped by a forklift?

From the video in this question, you can see a bunch of stable shelves that are bumped by a forklift. This causes a domino effect, but unlike a regular domino falling over, there is clearly a buckling ...
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2answers
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Finding 3 unknowns in 2D-collision problem [on hold]

While solving a 2D-collision problem, I obtained the following 3 equations: $$0.866\,|\vec v_{Af}|+|\vec v_{Bf}| \cos \theta_{Bf}=6$$ $$0.5\,|\vec v_{Af}|+|\vec v_{Bf}| \sin \theta_{Bf}=0$$ $$|\vec v_{...
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1answer
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In the SHM equation $F= -kx$, $k =mw^2$ why not use $mf^2$ where $f$ is frequency $w$ here comes out to be $1/s$ not $\text{rad}/s$?

The reason I am stating this is because on calculating the units of w(omega) I found is equal to s^-1 not regular the rad/s. Proof: ...
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5answers
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Why does energy conservation give me the wrong answer in this inelastic collision problem?

Suppose there are two objects. The first object is stationary and has the next parameters: v1=0 m/s, m1= 4kg. The second object is heading towards the first one with speed v2= 8m/s and mass m2= 60 kg. ...
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2answers
90 views

What is exact definition of potential energy if all forms of energy except kinetic comes under potential energy? [duplicate]

I need to know the exact meaning of potential energy. I AM confused what it actually means.They say all types of energy comes under 2 types kinetic and potential so what is potential energy then? My ...
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1answer
17 views

Equation for $N$-body problem using Jacobi Coordinate

For reference on Jacobi Coordinate used for solving 2-Body problem, I referred Wikipedia Jacobi Coordinate, and on looking at those equation I can't get the meaning of the symbol q in the equation for ...
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1answer
26 views

Stress and Strain in a standing wave

Where are stress and strain maximum in a Standing wave? what about a transverse wave? My book says "strain is maximum at the nodes in a standing wave". But since Antinodes are the position of maximum ...
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0answers
30 views

What happens if you hit street furniture with a car? [on hold]

would you be able to drive on or get stranded? I played GTA 5 and it takes a long time before the car is total loss after it has hit a lot of street furniture.
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1answer
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Question about the angular speed of a rod as it falls to the ground [on hold]

I was given a problem yesterday in which a bird flies into a rod and then is stunned. It gives the rod some initial angular speed (found through conservation of momentum). However, my TA then claims ...
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3answers
33 views

What makes a skier turn when weight is applied on the front-inner side of the outer ski?

A downhill skier is on the slope indicated by the arrows (arrow head indicating the direction of the incline). The skier has nearly reached the left edge and wishes to turn. The skier is heading, ...
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1answer
32 views

Do pulleys have no effect on atwood machine?

I was given the following example for an atwood machine: We should calculate the accelaration of the masses. The given solution to this problem was the same as like there is just one pulley: $$a=\...
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3answers
85 views

What makes displacement a vector?

Displacements are vectors because they add like vectors is the answer. It is also an experimental fact. Though rotations are displacements but not vectors. Is there any more fundamental or intuitive ...
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1answer
79 views

Can a projectile bullet kill? [on hold]

Today, I was watching a movie, in which a person shot a gun in air. The bullet went high in sky, became stationary for a moment and dived back and killing a non-innocent person by hitting him in head ...
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0answers
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A slight loosely fit window is balanced by two strings which are connected to the weights $w/2$ each [on hold]

The strings pass over the frictionless pulleys as shown in the figure. The strings are tied almost at the corner of the window. The string on right is cut and then window accelerate downward .the ...
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0answers
58 views

Find number of collisions [on hold]

A ball dropped from a certain height,falls in the influence of uniform gravity,strikes the ground and rebounds elastically.During a time interval t=8s from it was dropped,it covers a distance s=20m....