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 are the major differences in group-skydiving as opposed to “single” skydiving?

Surface area/the cross-sectional area is greatly increased, so my thinking is it should decrease terminal velocity as well as a couple of other factors. But mass changes too (since there would be more ...
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194 views

Kinematics equations of motion find x position in 2D from height

I have a question and I thought of 2 possible ways to answer it however the resulting answers are different which means I must be doing something wrong in my calculations. All the below happens 2 ...
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100 views

Why and how is acceleration absolute?

Is there a testable model which explains why rotation of an object in space and straight-line acceleration appear to be absolute while uniform translation is relative? I know of Mach's explanation, ...
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100 views

Motion of a wheel with an added mass to its edge [closed]

Imagine a wheel with homogeneous mass distribution, but there is a mass concentrated to its edge at a specific point. The wheel is rotating over a horizontal surface with a given initial velocity. How ...
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3answers
2k views

When is tension constant in a rope?

Suppose we have a massless rope with pulling forces applied at each end. In which scenarios is the tension in the rope constant throughout? For example if there is a knot in the rope the tension is ...
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893 views

Force and direction of velocity

If the angle between force acting on a particle and velocity of particle is zero degree, the value of velocity will increase. If this angle is 180 degree, the value of velocity will decrease. If this ...
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92 views

What logic did Newton give in support of using relative spatial measurements? [closed]

The crux of space-time is that it is one thing to have abstract concepts of absolute space & time,and it is other thing to describe the actual motion of an object in terms of measured changes of ...
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1answer
122 views

Is there any net external force acting on the universe?

If we consider the universe as a system, is there any net external force acting on it? I am thinking of whether or not the center of mass of the system moves. If there is no such a net external force ...
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1answer
183 views

Moment of Inertia and Linear Dimensions

For similar solid bodies made from constant density, how does the Moment of Inertia about a particular axis vary with linear dimensions? This is from an school textbook. I have covered all of MI ...
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Is work done = change in KE, or change in mechanical energy?

Starting from $F = ma$ we get: $$ F=m\frac{dv}{dt} = m\frac{ds}{dt}\frac{dv}{ds} = mv\frac{dv}{ds} $$ which leads to the work done: $$ W = \int Fds = \int mvdv = m\frac{v^2}{2} - m\frac{u^2}{2} ...
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314 views

Work done: kinetic energy or area under F-ds curve?

Starting from $$F=ma = m \frac{dv}{dt} = m \frac{ds}{dt} \frac{dv}{ds} = m v \frac{dv}{ds}, $$ leads to work done = integral of F.ds = integral of mvdv = change in KE. Suppose a variable force is ...
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380 views

Rotational Inertia of a Disc and Subsequent Acceleration

This is more of a conceptual problem as opposed to anything wrong with the maths! (I think/I hope! :) ) But essentially the problem states: imagine a circular flat disc of radius $R$ and of mass ...
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46 views

Transformation for rotating frame [duplicate]

Can anybody please explain the derivation of transformation of a frame rotating with constant angular velocity w.r.t. a stationary frame. It can't understand it from my book. The derivation started ...
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3answers
255 views

Centripetal and centrifugal force

If a stone is rotated with the help of a rope, then both centripetal force and centrifugal force will be liberated. The magnitude of that forces are same, but direction of them are opposite to each ...
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97 views

Forces acting on a body-slope system

Suppose you have a wedge on a table with length $l$ and mass $M$. The angle between the slope and the horizontal direction is $\alpha$. You also have a point of mass on the top of the wedge with mass ...
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Will relativistic glider cause lower gravitational force in Newtonian gravitation?

In the articles The relativistic glider and The relativistic glider revisited, the relativistic glider is proposed where a quasi-rigid body can slow down its fall under gravity without any reaction ...
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64 views

Intuition of centrifugal force [duplicate]

I heard that centrifugal force does not really exist; that it is made as opposite substance to centripetal force. Is it true? Could someone define for me what centrifugal force is in terms of vectors ...
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1answer
181 views

Normal force on object on a curved 3D surface

Let's imagine we are on the top of some axisymmetric surface. Let it be $r = r(z)$ in cylindrical coordinates $\left(r,\varphi, z\right)$. It can be a sphere, which we have discussed in my previous ...
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Why does the pressure sensor give the same value of pressure no matter how it is oriented?

Let a small pressure-sensing device be suspended inside a fluid-filled vessel. ... We find by experiment that at a given point in a fluid at rest, the pressure has the same value no matter how the ...
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102 views

Which formula is correct for the velocity of a mathematical pendulum?

Suppose I have a mathematical pendulum swinging in a plane, and the angle between the vertical direction and the pendulum is $\phi(t) = \phi_0 \cos\omega_0t$. The length of the pendulum is $l$, its ...
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60 views

I can make the mechanical energy 0 or in fact anything. Is this normal?

We let the rope fall with $\alpha = \pi/2$ (no initial velocity). if I choose the original of potential energy as the picture indicates there, this means that: $$E_m = E_{pe} + E_c = \frac12mv^2 ...
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1answer
72 views

A parameter to quantify instability in flight

Suppose I have plotted the body angles of a flying aeroplane.I have two such plots. One of a normal plane, and the other plot in which a primary sensor of the aeroplane is removed. So with the absence ...
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391 views

If reality is relative, then what about Newton's bucket argument?

There is nothing outside the universe. - Lee Smolin So, there can't be any absolute frame. Everything must be measured relative to an entity that exists in the universe. Thus, space ...
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82 views

Boy , Table and the Newton [duplicate]

Suppose a boy is trying to stand on a table. If the table can hold upto a particular force, the boy would fall on to earth. If he stands on the table and providing greater force than the table can ...
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1answer
184 views

Reversibility in classical mechanics

I am watching Susskind's 'Theoretical Minimum' videos. At one point in his course on classical mechanics (2nd video if I remember correctly) he affirms that Netwon's second law of motion makes ...
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128 views

Transmissibility

An extract from a school maths mechanics textbook reads: To deal with cases in which the body is not rotating freely under gravity, we need to take into account also the work done by other ...
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1answer
378 views

Resemblance between Coriolis force and magnetic part of Lorentz force

If we interchange velocity with charge and omega that is rotation of a system with $B$, magnetic field, we get the same thing. Is there any deeper meaning to this same mathematical form?
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What is the difference between Newton's first & third law?

Newton first law states that object stays in fixed state, unless external force is applied. Newton third law states that: if there is action then there will be opposite & equal reaction. So if ...
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3answers
93 views

About Kepler's Law

When Earth goes near the Sun, its velocity increases and when it goes far from the Sun its velocity decreases. Then why according to Kepler's law is the time period $T^2 \propto a^3$, where $a$ is the ...
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1answer
272 views

Parallel axis theorem

For this question we are working in 2-D space. Let's say that we have an arbitrary body. I know the inertia with respect to a perpendicular axis (to the body, that is) that passes through a point (A). ...
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1answer
147 views

What arguments and examples did Newton give in support of Absolute time and space?

As everyone knows, Sir Newton advocated the Absolute Space & Time theory. But what examples and arguments did he confer to establish his theory? I read the wiki page where it was written that he ...
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1answer
246 views

3 pulley and 2 masses,relation between their accelerations [closed]

I want to find acceleration of each mass in this system. lets take length of rope between three pulleys as $L$. then we can use this relations ...
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1answer
114 views

An unwinding cable problem [closed]

Suppose a light cable is wrapped around a solid cylinder with mass $M$ and radius $R$. The cylinder rotates with no friction about a stationary horizontal axis. The free end of the cable is attached ...
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What are absolute space & time? Why are they not absolute in reality?

As said by A.P. French in Newtonian point of view: Space is a sort of stationary three-dimensional matrix into which one can place objects or through which objects can move without producing any ...
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4answers
601 views

Why are we still teaching Newtonian physics if it's “false”? [duplicate]

Why are we teaching an outdated theory when the math in general relativity isn't that hard? I really don't see a reason why we should teach a highly oversimplified theory in our schools. For me, it's ...
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536 views

Do objects really move in the direction of the force applied?

According to the second law of motion: Direction of the force is in the direction of change in momentum. Now, I came before a problem. Though an easy one, I was perplexed at a point. A ...
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1answer
873 views

The subtle differences between angular momentum and centrifugal force?

I am a mathematician wanting to understand the differences between the concepts of angular momentum and centrifugal force. The following two ideas are clear to me from a physical point of view, but ...
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63 views

Can someone please explain the forces acting on the rod? [closed]

Can someone please explain the forces acting on the rod.
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1answer
312 views

Equation of Trajectory [closed]

I was reading about Lorentz force law and motion of a charged particle under Electric field or magnetic field and I understood how they move in it. But as I was moving further I came across the ...
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2answers
116 views

Reasons for decaying orbit for satellites and spacecrafts

As per newton's law, unless a force is applies, moving objects will continue to move in a straight line. A satellite which speeds at around 17.5k mph would be travelling in a straight line considering ...
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How, exactly, does a reaction wheel work?

Reaction wheels, mounted on spacecrafts and satellites, are used for precision attitude control. It is not clear to me how they can do this, though. My best guess is that when a motor accelerates a ...
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2answers
893 views

A precise definition of macroscopic and microscopic objects

What are the formal definitions of "macroscopic object" and "microscopic object". How can one differentiate between them? I mean, is there any fixed condition by which we can distinguish between them? ...
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52 views

Inclined pulley. Finding the $\frac{M_1}{M_2}$ [closed]

Problem As you can see in the picture, $M_1$ and $M_2$ are attached by a massless rope over a pulley. the height difference of $M_1$ and $M_2$ is $h$. The masses start to move and after $τ$ seconds, ...
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1answer
207 views

Conditions of friction on constant acceleration [closed]

If a body is moving with constant acceleration, then what would the frictional force be? Zero In forward direction, In reverse direction all of above
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68 views

Can a projectile moving at supersonic velocities leave a silhouette in whatever it hits?

I was recently reading this, and Floris's answer confirmed my knowledge that the information of an collision travels at the speed of sound. While I was thinking about that, my mind wandered and I ...
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2answers
143 views

Understanding variable mass equation for mass ablation/ejection

The "Variable-mass system" entry in Wikipedia, under the "Mass ablation/ejection" title, shows: $$p_2 = (m+dm)(v+dv) + u(-dm)$$ The parameter $p_2$ is for the momentum at $t+dt$, meaning $p_2 = ...
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1answer
34 views

Conservation of generalized energies in Newtonian and Relativistic Systems

I was considering the following problem: In a closed system, it is assumed that mass, momentum and energy is conserved. If we label the total mass of the System $M(i)$ at a time i, the total Momentum ...
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1answer
105 views

Running Euler's disk in a superfluid

I was considering the toy Euler's Disk, a video can be found here: http://www.youtube.com/watch?v=mVl2CBG_h2s I was interested in understanding the behavior of the disk particularly in vacuum and in ...
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1answer
51 views

Making water spin a wheel [closed]

Let's say that I have a wheel with 8 symmetric arranged rectangular plates of area $A$ and the water, with density $\rho$, in the river it moves with $v\: \mathrm{m/s}$. How do I calculate the ...
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1answer
36 views

Do two engines with the same specific impulse always perform the same amount of work?

As the title say, do engines with different thrusts with the same $I_{sp}$ and the same amount of fuel perform the same amount of work?