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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1answer
147 views

Fluid dynamics tsunami

I have been given a energy head (pressure) in meters for a given tsunami on land. If the tsunami hits a wall 1 meter by 1 meter, is it possible to calculate the height it will reach. I am thinking it ...
8
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4answers
800 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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2answers
944 views

Calculating torque in 3D?

Say you have a sphere, and you have several torque vectors acting on it, all at different points. Say you have the vector (6i + 3j + 5k) originating from point A, and the vector (3i + 1j + 9k) ...
3
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1answer
244 views

Acceleration: A ball sliding down the inside of a semicircular bowl

Edit: To clarify, this is a homework question. But I couldn't care less about getting the answer to this specific question as it's not even assigned yet. It looks interesting and I want to understand ...
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3answers
53 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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2answers
60 views

How to calculate acceleration of the elevator? [on hold]

A man of 80kg stands on a spring balance in an elevator. When it starts to move the scale reds 700N,calculate the acceleration of the elevator and identify the direction of the elevator
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1answer
39 views

Circular motion from rest [on hold]

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 ...
3
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8answers
1k views

Dying question: Tractor wheels — large vs small

This question has stumped me for over a month now: Why is it that a tractor has large wheels at the back and small wheels in the front? Current ideas: small wheel in front --> lower center of ...
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1answer
27 views

Parabolic slide [on hold]

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
37 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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0answers
14 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 ...
-1
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0answers
47 views

Center of Mass of Snowman [on hold]

Suppose you build a snowman 6 feet tall by stacking 3 spheres. The bottom sphere has a diameter of 3, the middle one a diameter of 2, and the head a diameter of 1. What is the center of mass?
0
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1answer
61 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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3answers
432 views

How can I relate linear and angular motion using a single formula?

I want to relate linear and angular motion using a single formula. Assume I have a 10m rod, and I apply a force of 5N on it, 2.5m away from the axis of rotation for 1s. How can I determine the ...
0
votes
1answer
31 views

How do we find the cone angles of the conic sections that are the Newtonian orbits?

In planetary motion, when the eccentricity of a conic section and its semi-latus rectum are known, how do we find out the cone's semi-vertical angle and angle of cutting of the cone by plane?
0
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1answer
34 views

Free fall actual motion direction on the rotating earth [on hold]

I've calculated that the actual acceleration that a body experiments taking into account the gravitatiotional atraction of the earth and the centrifugal pseudo-force is given by: ...
1
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1answer
29 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 ...
4
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5answers
2k 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 ...
0
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2answers
50 views

Movement of accelerating points with maximum speed (i.e. running away from tiger) [on hold]

I'm walking through a forest and suddenly I see a tiger. And now I have a problem. I want to know how much time I have left but I don't know how to calculate it. Or more formally: Let's ...
0
votes
3answers
70 views

Object Pushed by Multiple Forces [duplicate]

If we have a general object and we have multiple forces acting on it at several points. Assuming we know the center of mass, mass and moment of inertia of the object: Will the object rotate only ...
2
votes
2answers
214 views

Loads in decelerating a falling object

I remove trees in confined spaces setting up rigging systems, I am keen to look at the science behind it in more depth so far the formulas that I have found don't take into effect the ongoing effect ...
1
vote
1answer
21 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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3answers
141 views

What position of the center of gravity can make the front wheels of the car lift off the ground?

I have a question regarding the position of center of gravity required to just lift off the front wheel of a vehicle Consider a vehicle of mass $m$ having a center of gravity at height $h = 0.5m$ ...
0
votes
1answer
48 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: ...
9
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2answers
2k views

Put a bullet into orbit around the moon

While I was watching this beautiful video, the absence of air friction pushed me to ask myself: While standing on the surface of the moon, what is the initial velocity by which you can fire a bullet ...
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2answers
54 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
64 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
31 views

Speed, weight and force [on hold]

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 ...
1
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2answers
172 views

“Skidding” to Brake on a Skateboard

When people are skateboarding, sometimes they kind of push out their back foot when they turn while carving, causing the board to skid a bit. I was wondering the physics behind this, any details on ...
6
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3answers
334 views

Optimal speed for the water wheel

The hydroelectricity plants extract the potential energy of highly deployed massive object (water) as it falls down. Without turbine, all that energy would be converted into speed (kinetic energy) at ...
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1answer
2k views

Why is the mechanical advantage of a wedge = length of slope/ width?

Mechanical advantage is defined as Force Output/Force Input For a symmetrical wedge with the length of the slopes being equal and the width being the distance between the end points, the articles ...
0
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0answers
29 views

Incline plane problem [on hold]

A string carrying a $5\times10^{-2}$kg bob hangs from the roof of a vehicle. It moves down an incline at an angle of $30 °$ with the horizontal with acceleration of $3\mathrm{ms}^{-2}$. What angle ...
2
votes
2answers
13k views

What is the relationship between Force and Kinetic Energy?

I am an Middle-School (Grade 8) student, who is self-learning classical mechanics. I saw this equation from Classical Mechanics: $\vec F=m \vec a$, the following equation is pretty straight forward ...
0
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1answer
23 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 ...
0
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1answer
64 views

Normal force, work and conservativity

I have searched very much on line, both in this site and elsewhere, but found no proof of whether the normal force is conservative or is not, in general. Clearly, if the force is orthogonal to the ...
8
votes
3answers
683 views

Energy needed for Superman to take off and fly at the speed of sound

I just watched "Man of Steel", and I'm wondering if my logic is correct. Let's assume Superman is 80 kg. The energy required to take off from the rest to reach the speed of sound in air (if I neglect ...
0
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0answers
41 views

STEP problem (2004 paper II, mechanics)

This question says that the force exerted on a train (by its engine) when it is moving with velocity $v$ is $Pv^{\frac{3}{2}}$ where $P$ is a constant; and at velocity $v$ the resistance is $kv$ where ...
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0answers
24 views

Circular Motion [on hold]

How do I prove the last part? I have no idea how to start.
1
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2answers
200 views

Confused about elasticity and collisions

I was solving the following problem and the explanation to it confused me. There are two objects with mass $m$ and $M$, respectively. The object with mass $m$ has a velocity of $\sqrt{2gl}$ and ...
0
votes
1answer
109 views

If we dropped an object into the Pacific Ocean, would it completely sink to the bottom of the ocean floor or not?

Obviously if the density of the object is smaller than the density of water it would not sink at all. But I was thinking that, even if the density of the object is greater than the density of water, ...
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vote
0answers
25 views

Rain falling into a cart on an incline [on hold]

I have a practise question in which a cart on and incline of angle $\alpha$ and starts initially at velocity $v_ 0$. Just as the cart moves off it starts raining vertically and the mass of the rain ...
0
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2answers
30 views

What theories or formulas are involved with velocity

What theories or formulas are involved or can be added as background information in an experiment that sees a small toy car roll freely down an incline where the surface area is altered to cause more ...
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2answers
78 views

What is causing the normal force in circular motion?

In the picture, at point 2 (the bottom of the ramp) the normal force of the object has a greater magnitude than weight. I understand that the normal force has to be greater than the weight since the ...
0
votes
1answer
63 views

The correct integral for Newton's shell theorem

I am trying to prove Newton's Shell Theorem, and the natural integral I think of to use does not seem to give the right answer, so I am trying to find my mistake. For simplicity, I will work in one ...
2
votes
2answers
64 views

Lack of rigour in usual derivation of Work-Energy Theorem

The derivation of the Work-Energy theorem usually goes as follows: You define the work done on a particle under net force $\vec{F}$ as $$W=\int\limits_C \vec{F}\cdot\mathrm{d}\vec{r}$$ And then you ...
1
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0answers
60 views

Bicycle gyroscopes [migrated]

I've been having this idea for some time but never worked it out properly, mainly because I lack the required engineering knowledge. I wondered if it would be possible to convert the energy you ...
2
votes
2answers
48 views

Why does the period/frequency of a fan slow down significantly when I taped a piece of rubber band to it?

All of this was done with a standing fan set horizontally on a table. During an experiment, I had to tape a piece of rubber band to one of the standing fan's blade and measured the period of the fan. ...
0
votes
1answer
56 views

What is “adjustable constant”?

This is quoted from A.P.French's Vibrations & Waves. Explicit differential form of linear harmonic oscillator is: $$ m\dfrac{d^2x}{dt^2} + kx = 0 \quad \& \quad \dfrac{1}{2} ...
3
votes
3answers
7k views

Does a car use friction to move?

When a car's engine injects fuel into the cylinder chambers, the reaction creates a force that generates rotational momentum to the shaft and over the transmission, it translates that power to the ...
0
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2answers
114 views

Why do termite pellets fall in a perfect circle?

I was just wondering why termite pellets fall down from my bed in a perfect circle. You can see from the images that the follow down on the floor making a perfect geometric figure which is void in ...