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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Gravitational Collapse

Consider a spherically symmetric cloud of mass $M$ with radius $R$ and uniform density $\rho$. The gravitational collapse is governed by Newton's second law \begin{equation} \ddot{r} = - ...
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2answers
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Why does the ball lose contact if it has velocity great or less than $\sqrt{rg}$, while moving over a smooth sphere of radius $r$?

Let a ball of mass $m$ is given a velocity over the the top of a smooth sphere of radius $r$. The equation of motion at the topmost point will be $$mg - N = m\dfrac{v^2}{r}.$$ As $v$ increases, $N$ ...
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3answers
173 views

Is there any tension in a massless spring that connects two free falling bodies in different horizontal planes?

Two bodies A and B of same mass $m$ are attached with a massless spring and are hanging from a ceiling with a massless rope. They are in same vertical plane but not in same horizontal plane. Now the ...
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2answers
67 views

What force needs to be applied to produce twice as much acceleration as already present in a body?

Let the current body of mass $m$ be moving with acceleration $a$, produced by applying $F = ma$. So, I thought that if I apply force $F$ again (same magnitude and direction as before), I would get ...
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50 views

Please explain the integration [on hold]

the integration of (6 - 0.06s) should be (6s - 0.03s^2). Why is the solution (12s - 0.06s^2)? It seems its factored by 2 but I don't know the explanation to it. Cheers
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simple question on torques on an ellipsoid

I have an ellipsoid, and in the reference frame where the x-, y- and z-axis are aligned with its eigenvectors I compute the torque $\vec\tau$ acting on it. And I'm asking myself how can I quantify ...
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2answers
37 views

Connection between moment/torque and centre of gravity?

So I understand how moments work with regards to basic examples like pushing a door, in that the further you are away from the hinges of the door, the greater the moment, which is like a turning ...
5
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3answers
69 views

Why is a beam reach the fastest point of sail on modern sailboats?

I've heard that a beam reach (perpendicular to the wind) is the fastest point of sail on modern sailboats, but I haven't heard a satisfying explanation of the physics behind the claim. Triangular ...
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24 views

Why friction increases with increase in normal force? [duplicate]

Why is friction dependent on normal force and not the actual weight? I have also read that friction is horizontal component of contact force. Is this true?
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1answer
26 views

What does a scale accelerating on an incline read?

I was watching an online video lecture about dynamics, and then I came across this brain teaser, and I've been thinking it over for a couple of hours but can't seem to find the solution. I hope ...
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2answers
73 views

Conceptual question regarding work

Here is a problem I am having some trouble with: The solution is below, my question is, why is conservation of energy valid in this situation. From my understanding, just before the box hits the ...
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2answers
33 views

Collsion in 2D, find angle and final momentum

Suppose that the collision is completely inelastic. Disregard friction as the surface is smooth. Suppose that one is in the direction of $(1,0)$ and the other $(0,1)$. Is the final momentum the ...
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1answer
33 views

Athletics on the moon [on hold]

The moon is a lot smaller than the earth ($\frac{1}{81}$ of the mass and $\frac{3}{11}$ of the diameter). a)How high would a professional vaulter jump on the moon? Assume that he would jump ...
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1answer
31 views

Coriolis Effect vs airplane

So, if I build a highway from north pole towards equator and sit in a car, speed pretty fast towards it, I should feel force with the Earths rotation due to the different rotation speeds of this ...
2
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1answer
35 views

If I shoot a hockey puck on ice, is the force of me shooting it applied throughout its travel, or is it a one time force?

For example, if I take a slap shot on a hockey puck, from what I understand, the forces acting on the puck are friction, the normal force, and the puck's weight. And, since I'm not constantly either ...
2
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1answer
28 views

Force needed to roll wheel over edge [on hold]

I'm looking to find F. See image below. What we know: Mass of the wheel: $ m = 14 $ kg Wheel radius: $ r = 0.32 $ m What I've tried so far: $$ mg + N + \sin(38.7)k = 0 $$ Once the wheel ...
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1answer
24 views

Greater momentum than initial?

The question is : Heavier object A, initially at rest, is struck by lighter object B. Is it possible for object A to have a larger final momentum than the initial momentum of object B? The ...
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0answers
16 views

pascals law of liquids in terms of kinetic theory of molecules

Suppose a cylindrical container of base area A filled with water is carrying a piston on top. If the piston applies no force on the liquid, assume the pressure is P for a point located on the boundary ...
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1answer
73 views

How to explain this to my sir

We all know that $f = ma$. But for finding displacement, we always use: $$ s = s_0 + ut + \tfrac{1}{2} a t^2 $$ My sir, i don't know why for some reason uses this weird method: $$ F = ...
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0answers
45 views

A question about Undamped Vibration [on hold]

A small collar of mass 1-kg is rigidly attached to a 3-kg uniform rod length L = 1 m. Determine the period of small oscillations of the rod when (a) d = 1 m, (b) d = 0.7 m.
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0answers
18 views

What is the speed of the panel when the spacing between the plates increases [on hold]

Flat-panel capacitor WITH the surface area of $200 cm^2$ is connected to the voltage $1000 V$. One of the plates we start to move away from a constant force $5\times10^{-4}$ Newtons. the spacing ...
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3answers
71 views

in Newtons 3rd law, where does the second body get its energy to react?

A very basic question, and apologies if I have overlooked something obvious. In newtons 3rd law, presumably energy is transfered to the second body from the first body (which itself was subject to an ...
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2answers
1k views

How does a spacecraft enter Earth's atmosphere?

If Earth whirls around the center of our galaxy at some 220 kilometers per second, how can a spacecraft, which is much slower, enter Earth's atmosphere when returning from Mars for example?
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25 views

How to prove by symmetry that tension in a section of rapidly rotating wheel act tangentially?

Suppose a thin uniform wheel of radius $r$ is rotating rapidly about its axis; its spokes have almost negligible strength. According to the book, the centripetal force is provided by the tension ...
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1answer
56 views

Why can this question about Centripetal Force not be answered in this way?

Here is the question: "A car travels round a bend which has radius $100 m$ and is banked at an angle of $20°$ to the horizontal. The car is travelling at a speed of $30 ms^{-1}$. What is the least ...
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1answer
18 views

Period of a spring in SHM (simple harmonic motion)

An object with unknown mass M is hanged on a vertical spring with unknown spring constant K, the spring is in rest and is 14 cm from its normal point (if it didn't had the mass hanged it had less 14 ...
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1answer
13 views

Condition for sliding of two blocks placed one over another and connected by spring

A constant force F is applied to smaller mass till M slides. The spring constant is k. Now it is asked to find k. I'm confused with the condition at which the block will start sliding. Can ...
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0answers
29 views

Action-Reaction pair in case of rocket accelerating in space [duplicate]

I understand Rocket works on Newton's 3rd law. So there has to be action-reaction pair acting on two different bodies. I know rockets accelerate in space, where there is nothing. So now I want to ...
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0answers
12 views

Path of puck through a turntable

I was looking a problem which tells me to consider myself standing on the ground beside a perfectly flat horizontal turntable rotating with constant angular velocity w. Then I lean over and shove a ...
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2answers
43 views

Static friction and Kinetic friction

I can't seem to find this anywhere on the internet or on stack... Sadly. Very basic question: I have a block that is on a surface. The coefficient of static friction between the two is $0.3$, ...
2
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1answer
95 views

If the effects of gravity cannot travel faster than the “c”, does this mean we are only gravitationally bound by masses in our observable universe?

I'm 17 and fascinated by the differences and omissions Newton made in his equations of motion. However it makes sense that gravity can't travel faster than light because of the force-carrying ...
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1answer
22 views

Object moving with 2 linear accelerations

Say I have an object moving with an acceleration of 5 m/s$^2$. At a certain point X, due to some forces, the acceleration of the object changes from 5 m/s$^2$ to 2 m/s$^2$. Would this change in ...
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2answers
41 views

Best coordinate system for Projectile motion [closed]

What is the best coordinate system for describing the projectile motion? Rectangular coordinate system or n-t(normal and tangential) coordinate system.
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Simulating the rudder of a ship? [duplicate]

Assuming a calm body of water, what would be the correct way to calculate the force to turn a ship based on the angle of its rudder? I've read this post which I'm not fully clear on. For instance, ...
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2answers
82 views

Conservation of angular momentum - exercise [closed]

A sphere of mass $M$ is rotating with constant $w_0$ regarding the axis that intersects the north and south pole of the sphere. A bug of mass $m$ sits on the north pole and starts to walk along a ...
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Max speed of a turning disk for an object to stay at rest [closed]

A coin is at rest relative to a disk moving with a angular speed of w: The coin weighs 0.010 kg The distance of the coin to the center of the disk is of 0.20 m The static friction is of 0.45N ...
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0answers
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Finding displacement of spring [closed]

Q) A block lies on a horizontal frictionless surface, and the spring constant is $50\,\mathrm{N/m}$. Initially, the spring is at its relaxed length and the block is stationary at position $x=0$. ...
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5answers
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$F=ma$, so if acceleration is zero the force must also be zero?

I was just pushing a huge rock which I couldn't move at all. Given that the acceleration was zero as a result of my efforts, since $F=ma$, doesn't this mean that the force must also have been zero? ...
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0answers
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Sliding ladder kinetic energy in generalised coordinates [closed]

This is a problem from Hand and Finchs' Analytical Mechanics, in a chapter looking at holonomic constraints and generalised coordinates in Lagrangian Mechanics. A ladder of length $L$ and mass $M$ ...
2
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Conservation Laws and Isotropic Time

In most dynamics books I've read they refer to conservation laws and their associated symmetries. I know that the conservation of momentum is a result of the homogenity of space angular momentum is ...
2
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2answers
45 views

How can tangential acceleration from a radial force be explained?

A mass is attached to a rope, and put into a circular motion. If I pull the string from the center, the tangential speed of the mass will increase (by conservation of angular momentum). I am ...
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1answer
22 views

What can I say about a graph depicting orbit a particle has gone through? Acceleration VS friction

I have an orbit in which a particle is told to have gone through. There is a straight part, and a curved part. I am asked to mark the right statements, which are: a. Without any further data, there ...
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0answers
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Mechanical energy? [closed]

A particle of mass $2\,\mathrm{kg}$ is attached to one end of a model spring that is hanging vertically from a fixed point O. The spring has stiffness $4$ and natural length $1\,\mathrm{m}$. ...
2
votes
1answer
94 views

Moving Around Space Without Propellant [closed]

A mechanism as shown in following picture is floating freely in space. Concentrating on the main components first, which is the long rod in the middle with another 8 smaller rods connected to it, ...
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1answer
19 views

What is meant by “method of approximate numerical method” or “method of digital computer” for solving the differential equation of resistive force?

I was reading "motion against resistive forces" in Newtonian Mechanics by A.P. French; here is the excerpt: [...] In general, the resistive force $\mathbf{R}$ is is a function of speed, so that ...
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1answer
43 views

Maximum range of projectile from elevation, simply?

Let us say you have project a ball at velocity $u$ from a cliff hight $h$, and we want to find the maximum range of the ball. Ok so you could do this using equations of motion (for constant ...
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1answer
33 views

How is the kinetic energy of the wind transferred onto a lift based wind turbine?

The rotor blades of a lift based wind turbine are shaped like airfoils, so the wind flowing around them creates a lift force which in turn moves them around. From a thermodynamic viewpoint and like ...
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3answers
573 views

Can Lagrangian mechanics be justified without referring to Newtonian mechanics?

Are there any ways of justifying Lagrangian mechanics as a foundation of classical physics, without referring to Newtonian mechanics? In other words, what is the deeper reason or intuition why ...
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How does the elasticity of a ball influence its behaviour during collision?

The problem I am trying to solve is as follows: A football made of rubber with mass $m$ rolls on a table at speed $v$ and angular speed $\omega$ until it hits a player. Some sort of deformation ...
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1answer
62 views

Which point in the graph does a parachute open?

The diagram represents speed-time for a sky diver. He falls freely from an aircraft then opens a parachute and later lands safely on the ground. At which point did the parachute fully open? ...