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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Proof of Newton's second law [duplicate]

Is it possible to prove Newton's second law of motion, $F=ma$? Or is it just realized because of proportionality and the definition of a Newton of force?
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1answer
64 views

Analysis of a card pyramid

Here's an interesting question I thought of. Firstly, picture one of those card pyramids. Hopefully you know what I'm taking about when I say card pyramid, but basically you balance two cards up ...
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4answers
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Does a truck stop faster if the stack on the back of truck is stable or if it moves forward?

My question in the title might not be very descriptive so I am re-writing it here: If there is a truck in motion and it has stack of hay (lets suppose) on the back. Now if the truck comes to a sudden ...
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2answers
54 views

Why does friction act on a cylinder rolling on an inclined?

When a cylinder performs pure rolling while on an inclined plane, Why does friction act on the bottom point? In pure rolling the bottom most point is at rest, so there is no sliding over ...
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0answers
25 views

Mechanics - Rotational Inertia [migrated]

I am facing a problem solving a mechanical system which is shown in the scheme below. We assume that coupling of the two shafts is done with a clutch Equations: ...
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1answer
69 views

Why doesn't atmospheric pressure crush thick walled structures?

There is one thing that puzzles me: common explanation of why don't structures collapse under the enormous atmospheric pressure (~101300N/m^2) is that the force pushing from inside balances out the ...
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0answers
71 views

Interesting approach to Kepler problem

I won't go into the explanation of this idea, because it is explained in this blog post. In this paper, which was featured on John Baez's blog, $\frac {dt}{d\lambda}$ is given as $\frac r V$, where ...
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1answer
100 views

Weightless person in a cart on a rail [closed]

In a problem I'm trying to solve I'm having a conflict between my understanding and the proposed solution of the problem. In the problem, a cart of mass $m$ is put at rest in the start of a ...
3
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1answer
50 views

Determining straining force and reaction forces on a beam [closed]

A homogenous beam $OA$ with the length $4a$ and the mass $m$ can rotate in the vertical plane along a horizontal axis through $O$ and is kept in equilibrium by a wire running from the points A and C ...
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2answers
44 views

Centre of mass of a system of particles

If the centre of mass of a system of particles is at the origin, does this mean that if there is a particle on the positive X-axis, there must be atleast one particle on the negative X-axis? I feel ...
2
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2answers
130 views

If Earth and Jupiter are orbiting around Sun in same orbit, will they have same time period?

Let us suppose that Earth and Jupiter are orbiting around the Sun in same orbit, If we talk about at any particular point. (Which is not possible but for the sake of question) I was wondering that ...
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3answers
51 views

An elevator accelerating upward, tension increases in the rope to which a fish hangs inside the elevator why?

A fish is hanging in an elevator through a rope, when elevator accelerates upward the tension in the rope increases why? When elevator accelerates downward the tension in the rope decreases why?
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1answer
23 views

Inertia of a body cancells some amount of force?

If we have a block on a frictionless surface and we apply force F on the block to accelerate it, some amount of applied force will be cancelled by the inertia of the block am I right?
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1answer
46 views

Newton's Third law of motion: A hammer hits a wall vs. hits a tire

When we hit the wall by a hammer, Newton’s third law says that hammer applies force on the wall (action) and wall applies force on hammer (reaction) equal in magnitude but opposite in direction ok ...
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2answers
84 views

Where does the angular momentum of the solar system come from? [duplicate]

We inhabit a system with significant angular momentum: http://www.zipcon.net/~swhite/docs/astronomy/Angular_Momentum.html If our solar system formed by gravity gathering its material together to ...
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0answers
19 views

Spring limitation

Is there any limitation in acceleration and frequency of a spring. Please, imagine a horizontal spring with an object of mass $m$ attached in the free side and the friction is neglected. ...
2
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2answers
141 views

Dropping a weight onto a spring scale

Say I drop a 5kg weight from a height of 1 meters onto a spring scale like many people have in their bathrooms. On impact the scale will show a higher weight than 5kg. Question: Which quantities ...
0
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1answer
31 views

Angular velocity in central force field

For motion in a central force field consider a rotating reference frame, which is characterized by the Euler angles $\alpha$, $\beta$, $\gamma$ associated with the rotation of the frame of Cartesian ...
4
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1answer
73 views

General construction of equations of motion for free particles

I've got a question regarding the different Symmetrie-Lie-Groups of Newtonian Mechanics and special realtivity. Is there a canonical way to obtain the equations of motion for a free particle only by ...
2
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3answers
115 views

Distance traveled by a water jet

I helped my kid in a science fair project, where we punctured holes in a water bottle at various heights and then measured the distance traveled by the water jets before they hit the ground. The ...
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0answers
33 views

Free body driagram of box and plate with a friction force on a smooth surface

On a smooth surface we have a plate of 40 kg and on that plate a a box of 10 kg. Between the plate and the box there is a ...
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1answer
39 views

Newton's law for rigid bodies

Is newton's third law valid for rigid bodies? Say, if we have a bullet hit on a rod which is vertically placed on a rough floor. Friction is just sufficient sp that the rod rotates and does not ...
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0answers
37 views

The behaviour that saves more energy/ petrol when driving down-up-hill [closed]

This question is in a way a follow-up of this one: Can a car get better mileage driving over hills?, it is similar to that, is no engineering question and is in no way a homework problem, I'd like you ...
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2answers
38 views

Resulting force when bending plywood

My sister and I are working on a thesis in interior design on a plywood chair similar to the picture, where the red part bends. We are trying to work out how much the plywood would push back when a ...
2
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2answers
57 views

Work done by frictional force on a sliding block

A block slides across a table horizontally with an initial velocity $V$. The frictional force $F$ brings it to rest after its Centre of Mass covers distance $S$. What is the work done by the ...
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2answers
59 views

Free-Falling Object

How does the presence of air affect the rate at which a body falls? What is the rule for falling objects, when there is little or no air resistance?
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0answers
36 views

Calculating the 3-dimensional torque on a non-uniform rigidbody given the angular acceleration about its center of mass

Say I have a rigidbody, made up of several point particles with known masses and positions relative to the center of mass. How would I find the torque on this rigidbody given its angular acceleration ...
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1answer
86 views

When will the pringles can fall?

When I'm pushing a tall, cylindrical object stood on its end (like a Pringles can) I can push it near its bottom, and it will slide forwards, or push it near the top, and it will topple over. So, ...
3
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1answer
42 views

Why is energy in a system typically able to be described using quadratic expressions?

This might be more of an applied math question. Why is the energy of a system typically able to be described using quadratic expressions. Is there an underlying mechanic that drives this?
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6answers
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Can you ever exert more downwards force than your weight?

So, because I'm a hardcore person, I risked all this afternoon by going out in the wind, the rain and the cold to construct a willow den. Yes, it seems a menial task, but it was actually quite ...
3
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1answer
41 views

Average force for repeated elastic collisions

I was asked to compute the average force exerted by a rigid spherical ball (mass $m$) on the floor over time $t \rightarrow \infty$, in a situation where the ball is dropped vertically from a height ...
2
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0answers
28 views

Distribution forces

I've got two trees and between them is a rope. When someone about 100kg sits at the center of the rope, what are the forces on both parts of rope (to the left-hand side from the person and right-hand ...
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0answers
23 views

Does relativity in any way “disprove” Newton? [duplicate]

I was reading a science magazine and it claimed that Einstein's theory of relativity disproves all of Newtonian physics. I was highly skeptical because all we have been learning at school is Newtonian ...
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1answer
34 views

Working out length of taut rope orbiting the earth remaining straight and radially directed [closed]

A taut rope is orbiting the earth with angular velocity $a$. It remains straight and radially directed. If the midpoint is located at radius $r$, find the length of the rope. I can't even imagine ...
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3answers
77 views

On a scale, why does the heavier object go down?

When you balance a pencil on your finger, I have always wondered, "Why does the heavier part go down, and the lighter, up?"
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1answer
38 views

Does mass distribution/center of mass affect free fall?

An everyday is example would be cars. If you were to drop a car, not taking air resistance into account, would a front-heavy car tumble forward as it fell? And a car with a perfect 50/50 front/rear ...
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4answers
867 views

Paradox in applying Newton's second law [duplicate]

Suppose I apply two vertical but opposite forces with the same magnitude in a body like is shown in the picture: According to newton's second law, the center of mass shouldn't accelerate, since the ...
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1answer
35 views

Parabolic slide [closed]

Can you give a big hint for this problem please? A material point is released at the end of a track in the form of a vertical arc of parabola $y = x^2$ in $[-1,1]$, the meter is selected as a unit ...
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1answer
46 views

Circular motion from rest [closed]

A particle $P$ is suspended from a fixed point $O$ by a light string of length $a$. When hanging at rest under gravity at $A$ it is given a horizontal velocity $u$. The particle moves freely in a ...
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3answers
72 views

Work-Energy conservation with friction

I didn't go to the lesson of work-energy theorem, so I miss something about this subject. I know the formulas, but I can't figure it out. This question has many quantities. Here is the problem, ...
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1answer
98 views

A moving brush on a vibrating surface

Hi group, I am a HS student in China preparing for a regional Young Physicist Tournament even. We are very puzzled about why would there be such movement. We would be grateful to see any inspiring ...
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1answer
35 views

Computing Acceleration in mass and pulley system using conservation of energy

I have a question in which a multiple pulley and mass system is being analysed. I can compute accelerations and Tension without any issue using newtons second law. However I am asked to use ...
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1answer
42 views

What is the position as a function of time for a mass falling down a cycloid curve?

In the brachistochrone problem and in the tautochrone problem it is easy to see that a cycloid is the curve that satisfies both problems. If we consider $x$ the horizontal axis and $y$ the vertical ...
0
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1answer
71 views

What makes the equations of motion dependent on each other?

When Galileo put forward the proposition that the motion of a projectile analyzed into separate horizontal & vertical parts, he made a great contribution to the conceptual basis of mechanics. ...
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1answer
22 views

Deriving the equation for the speed of a block down an incline using work - keep getting the wrong constant

So the question is: There is a block of mass $m$ travelling along an incline that makes an angle $\theta$ with the horizontal. If the block is pushed up the incline with an initial velocity $v_o$, ...
0
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1answer
50 views

Finding the equation of motion

I am currently working on a problem where a particle of mass $m$ can move along the x-axis with no friction. The particle is moving in a gravitational field and the potential energy is given by: ...
0
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2answers
68 views

Why doesn't a magnet on a refrigerator slide down?

Obviously gravity pulls objects towards the earth's surface. Now suppose I have a refrigerator and a magnet. The magnetic force is perpendicular to the gravitational force. So it is not counteracting ...
0
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1answer
79 views

Physics behind this drunken ball

I am trying to understand the physics behind this drunken ball: There is a wight inside the ball as he mentions, but where, at what position ? ...
0
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1answer
41 views

Speed, weight and force [closed]

If a road roller of weight $W$ is rolling on the road at the speed of $X\,\mathrm{kmph}$, how much force does it apply on the surface of the road (considering a sampled surface of the same size as ...
0
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1answer
33 views

How is a strength of a pull spread across two springs?

I started thinking about it when I came up with a puzzle which is probably way too elementary for this site, but it is hard for me to understand clearly. I just bought this small scale thing and I ...