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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What does Feynman mean when he says that $F=ma$ is not exact?

Chapter 12-2 in Feynman Lectures Vol. 1 states: In fact the law, $F=ma$ is not exactly true; if it were a definition we should have to say that it is always true; but it is not ... First, ...
2
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1answer
57 views

Falling off a chair, how best to save yourself

If I consider a man sitting on an office chair that reclines backwards iff you lean backwards. What could be done to prevent hin from falling? a) raising his legs till they are parallel to ground. ...
9
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6answers
1k views

Why can light (photons) bends in a curve through space without mass? [duplicate]

I've heard that light can form a curve if they travel near high-mass stars or even a black hole with strong gravity. Which is according to this Newtonian formula $$\large ...
4
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4answers
279 views

Is there work being done if no displacement occurs?

So the definition of work is $W = \vec{F}\cdot\vec{s}$. Say I have a point mass which is being pushed on both sides by equal forces and therefore does not move. Does this mean that no work is being ...
2
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1answer
73 views

Gravity vs inertia

As stated according to Newton laws of gravity, every object with mass attracts all other object with a force which produces acceleration. Basically there are several forces in the universe which ...
2
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3answers
845 views

Why doesn't static friction decelerate a rolling body?

I know that static friction isn't the cause of deceleration of a rolling body. But if static friction is the only force in the horizontal direction, then shouldn't there be some acceleration produced ...
2
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1answer
73 views

Relative strength of a dome

Is there a rough way to determine how the height of a dome affects the load that dome could support? For instance, assuming the bases of two domes are 24" in diameter, and one dome is 2" high while ...
0
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2answers
77 views

Animating an Acceleration Vector - Acceleration of object on a crested path in gravitational field

So I was reading in Chapter 3 of my textbook, Sears & Zemanksky's University Physics with Modern Physics by Young and Freedman, 13th Edition, and the discussion took us to a definition of the ...
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1answer
39 views

Why is the change in height for mass be $2h$ in this question? [closed]

Could anyone tell me why the height is $2h$?, and is the total gpe in a system where the masses are balanced 0?
0
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1answer
34 views

wall thickness for a very large, low-pressure vessel?

I'm working on a space colony simulation, and I'm at the point where I need to calculate the thickness of the habitat walls, as a function of air pressure and geometry (and assuming some common ...
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2answers
115 views

Why is $dr/dt= -V$

In the solution, it says we have $dr/dt= -V$ (polar coordinates) How? I can't see how this can be possible, we know that $r(t)=V/\omega(t)$, and that's it.
2
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2answers
73 views

Metric expansion of space and Newton's second law

I wanted to ask the following question: If the expansion of the universe is really accelerating, does that mean a certain force applied on the universe? (According to Newton's second law) What kind ...
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8answers
3k views

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?
4
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1answer
92 views

Why doesn't a wall move when you push it if there's space behind it?

In the first screen you can see that if a person were to push a wall within a typical household the wall would not move while keeping themselves tractioned to the floor. If you push hard and do not ...
2
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1answer
48 views

Walking & Swinging

How can I show that the most convenient way to move the arms while walking is swinging them back and forth, alternatively? To pose the question in another way: can I prove, starting from the ...
6
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8answers
405 views

How do we know that $F = ma$, not $F = k \cdot ma$

It seems intuitive that $a\; \propto \frac{F}{m}$, as the greater the force that is applied on an object, the greater its acceleration will be. Inversely, the greater the mass of the object, the ...
0
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2answers
73 views

Ballistic Pendulum Demo Problem

I have a question about the following problem: I got the solution $v=\frac{M+m}{m} \sqrt{2gh}$. But my real question is in the following picture: In the above slide, how can you derive ...
0
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1answer
107 views

Purely mechanical description of how gravity causes a gyroscope to precess

I know the vector equation that relates torque to moment of inertia and angular momentum. What I want to know is what physical mechanisms actually occur to keep the gyroscope from falling. Where is ...
-1
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1answer
74 views

Prove one of the following trajectories is circular

In his classical mechanics lecture, Prof Susskind gives a short exercise, which I "feel" is very simple, but don't know where to start with. The question is: "There is a coordinate system ...
0
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2answers
55 views

Who of these cyclist travel takes less time? [closed]

There are two cyclist. They start off with equal velocity $v_0$. The first one bikes a straight path, while the other bikes through a valley, something like this: We assume friction doesn't affect ...
-1
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1answer
25 views

Masses and Pulley

I have a two mass and a pulley system as shown here: I have the following two questions: First, why does $\dfrac{d^2}{dt^2} y_p$ is not zero, i I mean I don't understand why does $ y_p$ is going to ...
3
votes
1answer
48 views

Prerequisites for Halliday Resnick Walker

I am in grade 10. I have developed an interest in physics but unfortunately I do not know/ have not studied calculus yet as my school board does not recommend it in grade 10. I have a copy of ...
0
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0answers
33 views

Plank stopping time

Problem: A plank of length $L$ and mass $m$ lies on a frictionless floor, if the plank has an initial velocity $v$, what is the stopping time of the block if it meets a floor with friction constant ...
0
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0answers
41 views

Calculating size/weight of the base of a banner to withstand wind load [duplicate]

I want to build what is essentially a banner - a rectangular piece of fabric that will be mounted to a stand and displayed vertically. This object will be outdoors, so the most important factor in it ...
4
votes
3answers
84 views

What is an intuitive explanation using forces for the equatorial bulge?

The earth is not a sphere, because it bulges at the equator. I tried fiddling with centripetal force equations and gravity, but I couldn't derive why this bulge occurs. Is there (a) a ...
0
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1answer
50 views

Lift a weight with a pulley system

I have two weights, weighing one ten times the other. I should figure out a way to make a pulley system that can lift the heavier mass with the smaller one. I would like to use the least number of ...
39
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5answers
2k views

Is there a way for an astronaut to rotate?

We know that if an imaginary astronaut is in the intergalactic (no external forces) and has an initial velocity zero, then he has is no way to change the position of his center of mass. The law of ...
3
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2answers
32 views

Constraint and Applied forces

In D'Alembert principle forces are classified into constraint and applied forces ? Is this classification different from internal-external forces ?
2
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1answer
106 views

What are the determining factors for the velocity of orbiting bodies?

Please bear with me, as I'm not in the field of physics, this question may seem a bit simple. The scenario is the following; A specific stable orbit radius of a small body, say a satellite, to ...
0
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2answers
55 views

Why is work in a constant electric field equal to the force times distance?

Let's say, for example, that an infinite plate generates a constant electric field that exerts a force of 6N on a 1C charge. To move the charge from a distance of 5m to 1m from the plate, the work ...
0
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1answer
32 views

Initial conditions at Lagrange Points

I'm simulating the restricted three body problem. But I don't know how to found the initial conditions of the object located at the Lagrange points analytically or computationally. I mean my problem ...
0
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0answers
50 views

Illustrate the transition from linear to rotational kinetic energy

I wish to find an everyday situation that illustrates the following: A rod is moving in a direction perpendicular to its axis. One end "gets caught" and the rod starts rotating around this end. THE ...
1
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2answers
49 views

Why is the constant velocity model used in a projectile motion derivation?

I was re-studying university physics last week, I'm now in the chapter about kinematics in 2 dimensions and specifically the one treating projectile motion. In page 86 of his book (Serway - Physics ...
0
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0answers
30 views

What is a good mechanics book without calculus [duplicate]

I am very interested in physics and I want to improve my basics especially in mechanics. I have only started high school (junior) so I don't know much about calculus, which is used in most of the ...
2
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2answers
188 views

How do you travel in a circular orbit around a massive body?

I am trying to figure out how an object could achieve a perfectly circular orbit. Given a mass for the planet or other body the object is orbiting and a distance from the center of mass, how fast ...
0
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2answers
66 views

Why is the force of Friction less than the force applied on the block in this situation?

This is a seemingly basic mechanics problem but I'm having a dilemma in understanding what happens. You start with two blocks, one on top of the other (the bottom block has a larger mass than the top ...
1
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2answers
50 views

If and how are the Coriolis force and gravitation related?

I recently got into a discussion whether and how the Coriolis force/effect is related to gravitation. Is gravitation involved in the Coriolis force? If so, how could that be explained?
0
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1answer
126 views

Contradiction regarding friction of a rolling cylinder in an inclined plane

I came upon this while wondering whether the friction of a rolling cylinder on an inclined plane depends on the value of friction coefficient. now, $$f\leqq\upsilon N$$ Again after calculating I ...
4
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1answer
29 views

How does a (near) elastic collision work at a microscopic level?

Suppose a large mass $M$ travelling at $v$ impacts a small stationary mass $m$, then following through the elastic collisions from high school, we get that the smaller mass can exit the collision ...
8
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2answers
452 views

What will be different if the spring is not massless?

In almost all text, it uses the massless spring as example to illustrate the idea of elastic potential energy. I wonder what's really being changed if we consider the mass of the spring? I saw a ...
0
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0answers
51 views

Why does a particle in an accelerating vehicle does not 'forget' its initial velocity after being dropped out of the vehicle?

A vehicle is moving with some constant acceleration 'a'. A particle is dropped out of the vehicle with no initial velocity. The net acceleration of the particle as soon as it loses contact with the ...
11
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14answers
3k views

Is Newton's third law always correct?

Newton's third law states that every force has an equal and opposite reaction. But this doesn't seem like the case in the following scenario: For example, a person punches a wall and the wall breaks. ...
2
votes
1answer
33 views

How does separation of tracks affect the acceleration of a rolling ball on the tracks?

If I have two metal rods arranged like a ramp with coefficient of friction $\mu$, at an angle $\theta$ to the ground, and a solid metal ball or radius $r$ and mass $m$ rolling down between the two ...
1
vote
1answer
53 views

Motion of a car rounding a bank

When a car is traveling round a banked track as fast as possible, it has a tendency to slip up the slope. Opposite in the case when the car travels slowly and has a tendency to slip down. Can ...
2
votes
4answers
96 views

Losing mass in space

So I came across a question while studying laws of motion. Roughly, this is how it goes: There are two astronauts in a space shuttle, who together have mass 200 kg. If by doing exercise, they manage ...
0
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1answer
30 views

Kinematics and Energy - Finding the work done in projectile motion

If you are asked to find the work done by gravity on a projectile, the force will obviously be the mass multiplied by gravitational acceleration. What will the displacement be, the horizontal or ...
1
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2answers
67 views

How do I relate $\mathrm{d}s$ to $\mathrm{d}x$?

A block of mass $5\text{ kg}$ is kept on an inclined plane with angle of inclination $37°$, attached to a spring with spring constant $10\text{ N/m}$ kept at the base of the incline. The ...
0
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1answer
62 views

Force on a potentially rolling ball initially at rest

I'm a graduate student in mechatronics, but I give myself headaches on this astonishingly simple 2D problem. Imagine a ball (perfectly rigid) on an horizontal plane (perfectly rigid), initially at ...
0
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1answer
39 views

Tension when two connected blocks are pulled in opposite directions [duplicate]

Suppose there exist two blocks A and B connected by a massless, inextensible cord. Both A and B have equal masses and are acted upon by equal forces in opposite directions. So, is the tension in the ...