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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One strategy in a snowball fight
Here's a common college physics problem:
One strategy in a snowball fight is to throw a first snowball at a
high angle over level ground. While your opponent is watching the
first one, you ...
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Which direction will the yoyo move?
This question has been around the net for a while, and I haven't seen a good explanation for it:
A yo-yo is initially at rest on a horizontal surface. A string is pulled in the direction shown in ...
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How can kinetic energy be proportional to the square of velocity, when velocity is relative?
Let's start with kinetic energy (from los Wikipedias)
The kinetic energy of an object is the energy which it possesses due to its motion. It is defined as the work needed to accelerate a body of a ...
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Mass Needed to Clear an Orbital Neighborhood
In 2006 the IAU deemed that Pluto was no longer a planet because it fails to "clear" the neighborhood around its Kuiper Belt orbit. Presumably, this is because Pluto (1.305E22 kg) has insufficient ...
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Could a universe with purely Newtonian mechanics exist?
I've heard about the fine-tuning principle and how if the fundamental constants of the Universe were changed even a slight bit, life could not exist as we know it.
However, study on this subject ...
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Is the normal force a conservative force?
Most of the time the normal force doesn't do any work because it's perpendicular to the direction of motion but if it does do work, would it be conservative or non-conservative?
For example, consider ...
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What is the force on the arms in a pushup?
What force do the arms have to generate to do a pushup? Let us look a this simplified model:
The body can be represented by the green plank of mass B. Its angle to the ground is $\theta$.
This ...
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399 views
Equation for the trajectory of a frisbee?
I'm the lead programmer on a FIRST robotics team, and this year's competition is about throwing Frisbees. I was wondering if there was some sort of "grand unified equation" for Frisbee trajectory that ...
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What is the cause of the normal force?
I've been wondering, what causes the normal force to exist?
In class the teacher never actually explains it, he just says "It has to be there because something has to counter gravity." While I ...
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9answers
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How to explain independence of momentum and energy conservation in elementary terms?
I'm trying to explain to someone learning elementary physics (16 year old) that linear momentum and energy are conserved independently. I'm not a professional physicist and haven't tried to explain ...
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10answers
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Is the distance between the sun and the earth increasing?
M = mass of the sun
m = mass of the earth
r = distance between the earth and the sun
The sun is converting mass into energy by nuclear fusion.
$F = \frac{GMm}{r^2} = \frac{mv^2}{r} \rightarrow r ...
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Can you completely explain acceleration to me?
I understand what acceleration is, and I know the formula, and I understand it's a vector.
I just don't understand how the equation works exactly. I'm kind of picky, I know, but bear with me.
...
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How does the earth move?
My son who is 5 years old is asking me a question about how the earth moves around the sun. What answer should I give him?
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4answers
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What's the exact gravitational force between spherically symmetric masses?
Consider spherical symmetric$^1$ masses of radii $R_1$ and $R_2$, with spherical symmetric density distributions $\rho_1(r_1)$ and $\rho_2(r_2)$, and with a distance between the centers of the spheres ...
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When driving uphill why can't I reach a velocity that I would have been able to maintain if I started with it?
Consider these two situations when driving on a long straight road uphill:
Starting at a high velocity $v_h$, which the car is able to maintain.
Starting at a lower velocity $v_l$, and then trying ...
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2answers
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How is distance between sun and earth calculated?
How has the distance between sun and earth been calculated by scientists?
and size of sun?
Thanks,
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Why is a book on a table not an example of Newton's third law?
My textbook explains Newton's Third Law like this:
If an object A exterts a force on object B, then object B exerts an equal but opposite force on object A
It then says:
Newton's 3rd law ...
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2answers
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Is the gravitational potential of a planet in orbit always equal to minus the squared velocity?
Say a planet (mass $m$) is orbiting a star (mass $M$) in a perfect circle, so it is in circular motion.
$F=ma$ and the gravitational force between two masses $F=\frac{GMm}{r^2}$ so
...
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3answers
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Tidal force on far side
I have a question about tidal forces on the far side of a body experiencing gravitational attraction from another body.
Let's assume we have two spherical bodies $A$ and $B$ whose centers are $D$ ...
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3answers
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Conservation of angular momentum for a rigid body rotating about a fixed point
Picture a rigid body such as a sledge hammer. Imagine that the base of the handle is attached to a fixed point such that it can rotate but not translate. I give the hammer a good push to get it ...
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How does placing objects in liquids affect the mass?
I was dazing off in my physics class when I came up with this question and I was wondering about it all day. I could not provide myself with an adequate solution, so here I am asking the forum about ...
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Falling through the rotating Earth
Suppose you were standing on the rotating Earth (not necessarily Equator or the poles) and suddenly your body lost the ability to avoid effortlessly passing through solid rock.
Because the earth's ...
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2answers
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How does one explain this pattern generated by earthquake waving driving a pendulum?
How to explain this pattern generated by earthquake wave driving a pendulum? Specially, there are three groups of curves that look categorically different:
1) The group of curves outside the ...
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1answer
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What is the angle at which water is splashed when a vehicle tyre rides in water on the road?
I would like to know the following:
What is the angle at which water gets splashed when I ride my vehicle through a water on the road?
How does angle of water varies with speed?
What is the relation ...
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2answers
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What are the reasons for leaving the dissipative energy term out of the Hamiltonian when writing the Lyapunov function?
I have a problem with one of my study questions for an oral exam:
The Hamiltonian of a nonlinear mechanical system, i.e. the sum of the kinetic and potential energies, is often used as a Lyapunov ...
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What determines the angle of the cushion on a pool table?
If you look at the cushions (bumpers) on a pool table, you'll see that they're not vertical. They're tilted inwards. About 10 years ago, I came across a physics exam in which one of the problems ...
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Rope tension question
If two ends of a rope are pulled with forces of equal magnitude and opposite direction, the tension at the center of the rope must be zero. True or false?
The answer is false. I chose true though and ...
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11answers
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Why do we say that the earth moves around the sun?
In history we are taught that the Catholic Church was wrong, because the Sun does not move around the Earth, instead the Earth moves around the Sun.
But then in physics we learn that movement is ...
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4answers
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Can an object accelerate to infinite speed in FINITE time (Newtonian)?
Obviously this is impossible in relativity; however, if we ignore relativity and use only Newtonian mechanics, is this possible? How (or why not)?
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Is pushing actually easier than pulling?
It is generally assumed that pushing a cart is more easier than pulling one. But why?
Is there any difference in terms of force required to achieve the same amount of displacement?
Or is it just a ...
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3answers
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Kinetic energy with respect to different reference frames
I'm having problems understanding the following situation. Suppose two 1-tonne cars are going with the same orientations but opposite senses, each 50 km/h with respect to the road. Then the total ...
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4answers
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Why do we weigh less when falling?
I don't want to go to science world to find out because it would be a long round-trip.
I understand that acceleration/deceleration would effect the weight and I can also imagine that someone at ...
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2answers
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Why is there this asymmetry between the two foci of an orbital ellipse?
Why does the Earth revolve with the Sun at one of its foci? Does the other focus do nothing? Why is there this asymmetry in our solar system?
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Explanation that air drag is proportional to speed or square speed?
A falling object with no initial velocity with mass $m$ is influenced by a gravitational force $g$ and the drag (air resistance) which is proportional to the object's speed. By Newton´s laws this can ...
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Logical connection of Newton's Third Law to the first two
The first law and second laws of motion are obviously connected. But it seems to me that the third law is not related to the first two, at least logically.
(In Kleppner's Mechanics the author states ...
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Elementary derivation of the motion equations for an inverted pendulum on a cart
Consider a cart of mass $M$ constrained to move on the horizontal axis. A massless rod is attached to the midpoint of the cart, having a mass $m$ on its endpoint. See wikipedia for a picture and for a ...
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Slinky base does not immediately fall due to gravity
Why does the base of this slinky not fall immediately to gravity. My guess is tension in the springs is a force > mass*gravity but even then it is dumbfounding.
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Relationship between height and velocity in conservation of mechnical energy
I'm a high school physics student, and we recently did a lab on the conservation of energy where we measured the speed of a marble at varying heights on a rollercoaster track. We were supposed to ...
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1answer
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Shaping a wire such that a bead sliding on it has exactly isochronous oscillations
Let a wire be shaped according to some even function $y=f(x)$, with $f'(0)=0$ and $f''(0)>0$, and let a bead of negligible size slide frictionlessly on the wire. Let the bead oscillate ...
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How can a car's engine move the car?
Newton's First Law of Motion states that an object at rest or uniform motion tends to stay in that state of motion unless an unbalanced, external force acts on it.
Say if I were in a car and I push ...
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1answer
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How reliant is the Solar System on being exactly the way it is?
We know that all objects with mass exert forces on all other objects of mass such that
$$ F = \frac{GMm}{R^2}.$$
And as others have discussed the planets do interfere with each other ...
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Boy and box on ice
I have a troubles. Can you help me?
I have a task, called "slippery activity".
Boy (he has $m=45kg$) Stands at ice and tries to move a big box ($M=90kg$) with a string (rope). Boy's Slip ratio is ...
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2answers
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How Did Newton's Second Law Get Its Definition?
If I've read Newton's Laws of Motion correctly in the Principia, it seems that Newton attributed the "change in motion" (momentum) to the "impressed force". Mathematically this would be read as ...
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What in Newtons three laws of motion original to himself and not a paraphrasing of his predecssors
The three laws are:
First law: The velocity of a body remains constant unless the body is acted upon by an external force.
Second law: The acceleration a of a body is parallel[disambiguation needed ...
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Effect of the tail of the cat in the falling cat problem
To explain why a falling cat can turn by 180 degree without external torque and without violation of the conservation of angular momentum, one usually models the cat as two cylinders as in
...
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1answer
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Arnold´s Math Methods of Classical Mechs - a question on Newtonian Mechanics
There is the following question/answer on Arnold´s book Mathematical Methods of Classical page 10.
Arnold's Question A mechanical system consists of two points. At the initial moment their ...
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Aircraft nose-up glide
In the pilot's introductory book "Stick and Rudder" it claims that a nose-up glide is possible. It doesn't state how, why or when. It implies it's possible to do and maintain a constant forward ...
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1answer
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Kepler problem in time: how do two gravitationally attracting particles move?
Two particles with initial positions and velocities $r_1,v_1$ and $r_2,v_2$ are interacting by the inverse square law (with G=1), so that
$$ {d^2r_1\over dt^2} = - { m_2(r_1-r_2)\over |r_1-r_2|^3} $$
...
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Rocket launch from a mountain
If we were to build a high speed rail up the side of a mountain like in some ScFi movies, what is the velocity needed at the point of living the mountain excluding angular momentum from earth’s ...
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2answers
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How do objects change their axis of rotation?
If I hold a pencil at its end and spin it, throwing it upwards, it will spin about its end, but will soon start spinning around its center. How is this?
I would draw the following torque diagram for ...
