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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Lagrangian of three connected rods
There is free falling chain - 4 connected rods with mass m and length l:
...
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0answers
63 views
Rotating pipe with bug [closed]
A thin mass less horizontal pipe rotates about a vertical axis with angular speed $ω$ as shown in the figure. A small bug, located at a distance $r$ from the axis, starts crawling inside the pipe at ...
-7
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0answers
26 views
Mechanics Special Problem 4 [closed]
A block of mass M is pulled with a rope that exerts a force of a magnitude F, causing it to slide over horizontal ground with kinetic coefficient of friction μ (use "mu" when you input your answer). ...
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1answer
33 views
Question on static friction [closed]
This is the question, and the answer is given as 2).
Now my basic doubt is, are they asking us the direction of the total contact force on the object by the floor? Or, are they asking the direction ...
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0answers
17 views
What determines the motion in a Newton's craddle? [duplicate]
Let's say we have a Newton's cradle with five metal balls, each with a mass $m$. You pick up one and release it, and right before impact it has a velocity $v$. What determines weather the ball at the ...
1
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1answer
51 views
Mechanics question (a block on top of a block)
This question is very similar to this one here.
A block of mass $m_1$ is placed on another block of mass $m_2$ lying on a smooth horizontal surface.
The coefficient of friction (static and ...
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1answer
39 views
In Newtonian pressure, what type of function is force?
This is pressure in Newtonian mechanics:
$$P=\frac {dF}{dA}.$$
What does this mean?
(Doesn't it mean that force is a function of area?)
What type of function is force?
2
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1answer
49 views
Energy in a wind instrument?
My physics teacher said that he saw a guy playing a very large wind instrument on TV, and the guy apparently calculated that the total energy present in the instrument when he was playing was almost ...
3
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0answers
51 views
The secret behind the spinning, asymmetrically weighted, 2D disk-shaped top?
When you spin an asymmetrically weighted, 2D disk-shaped top, the heavy part actually rises to the top. Why is this?
http://www.youtube.com/watch?v=h0SZZTBQmEs
...
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1answer
23 views
Tension in parallel springs [closed]
A block of mass $200$kg is connected to a horizontal ceiling by four identical light elastic ropes, each having natural length $7$m and stiffness $180$N/m. It is also connected to the floor by a ...
6
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2answers
118 views
Confusion with derivation of fictitious forces
I read the mathematical derivation of fictitious forces on Wikipedia and I'm having trouble understanding it. I went on a few other sites looking for a better derivation, but they're all basically the ...
0
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1answer
36 views
History of Newtons law of gravitation
I have some questions about the history of Newtons law of universal gravitation.
Did Newton discover his three laws of motion before he discovered the universal law of gravitation?
I know two ...
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2answers
138 views
Newton Laws of Motion + Effective spring Constant [closed]
!
Can someone please help me in solving this question:
What is the effective spring constant for the system of the two springs, perfect pulley, and string shown on the left for it to be modeled ...
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1answer
125 views
Tension in a massless string around a pulley
A pulley having some mass has a massless string around it,with two unequal masses at the end of the string .Sufficient friction is present between pulley and the string such that the string does not ...
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0answers
20 views
air molicules repell
Why do air molicules repel each other? In working with airfoils I have found that air molicules repel each other. Gravity holds the air down as they push away from each other causing airpressure to ...
15
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4answers
393 views
+50
Why do whips hurt so much?
What exactly is the mechanism that makes a whip deliver such a strong impact? Elasticity, torque, or pressure? Just hitting something with a plank doesn't deal nearly as much damage. What's the ...
1
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2answers
42 views
Vaporizing ethanol from liquid
What is going on here http://youtu.be/LQFmKPA-iAg
Is ethanol leaving the liquid? If so, why?
Does the pressure add energy to the ethanol molecules causing them to gasify and move rapidly near border ...
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1answer
39 views
Understanding centripetal force vs frictional force diagrams?
I have an actual physics problem and also a conceptual question to go with it. From some test prep I was presented with this straight-forward question:
What is the minimum radius that a cyclist can ...
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0answers
31 views
Block over block Problem [closed]
There are two blocks one over the other , both on ground , masses are 2 kg for top one and 5 kg for bottom one , coefficient of friction between both is 0.8 and between lower one and ground is 0.2 . ...
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1answer
60 views
Solving differential Equation for the Two-Body Problem
So, I'm following the derivation in D. Morin, Introduction to Classical Mechanics, of the equations for a two-body system. I understand all of it, aside from this one step.
When he's talking about ...
0
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1answer
43 views
Newton's third law of motion, and the collapse of objects under heavier weight
Suppose a table is placed on earth. The weight of the table exerts a force on the earth say $10N$, then the earth will also exert a force of $10N$ on the table. If we place a truck on the table ...
1
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1answer
45 views
Proving Simple Harmonic Motion (direction of acceleration)
A particle of mass $m=0.5kg$, is attached to a spring of natural length $l=0.6m$ and modulus of elasticity $\lambda=60N$, and the setup is on a horizontal smooth table. The other end of the spring is ...
5
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1answer
80 views
How to derive the velocity in the double ball drop problem?
The double ball drop problem is as follows:
A ball of mass $m$ is placed on top of a ball of mass $M$ (where $m < M$), and the balls are dropped simultaneously from some height $h$. When the ...
2
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1answer
103 views
Is any work done when I walk?
I am trying to figure out the amount of work done when I walk X miles or for X minutes. So I got Work=Force x Distance and Force=Mass x Acceleration and Acceleration=(change in velocity)/time. I am ...
19
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3answers
347 views
How many points are required to make a black box
I have a black box with an arbitrary mass distribution inside it. I want to replace that object with n point masses without changing any mechanical properties of the box (center of mass, total mass, ...
3
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3answers
89 views
Static as opposed to Kinetic Friction in Rolling Motion
During analysis of rolling motion, why do we consider coefficient of friction as that of static friction and not kinetic friction?
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0answers
29 views
Find amount of force to move a 18 kg mass 0.1 seconds [closed]
Force is coming from two pistons pushing at 45 degrees applied to two adjacent corners of a square (0.6 m x 0.6 m) rigid plane. Mass of the plane is 18 kg. Piston stroke is 20 cm, piston bore is 40 ...
2
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2answers
33 views
Velocity in a turning reference frame
I often see the relation that $\vec v=\vec v_0+ \vec \omega \times \vec r$ in a turning reference frame, but where does it actually come from and how do I arrive at the acceleration being $$\vec ...
-1
votes
1answer
100 views
Newtons Cannon ball problem [closed]
Let's I have a Newton's Cannon ball of 15 kg and want to fire so it will round the earth and back to me.
My query is which law can evaluate the speed that cannon ball will revolve round the sun ...
2
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1answer
70 views
Understanding Kepler's problem
I wanted to know a few things about elliptical motion, that I do not understand so far.
Let's imagine that we have an attractive gravitational two body problem where both bodies carry out elliptical ...
2
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2answers
108 views
How to reconcile the two definitions of work? (mechanical and thermodynamical)
When studying classical mechanics, work is defined as: $W_M=\int F_{tot} \hspace{2 mm} dx$.
However, for thermodynamics, work is defined as: $W_T=\int -F_{ext} \hspace{2 mm} dx$.
I'm having trouble ...
0
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0answers
18 views
Stability of trajectory of disc which moves along a straight curve
Let's have a disc which moves along a straight curve on a plane in a uniform gravitational field. There need to discover the stability of it's trajectory.
I represented the possible deviation of the ...
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1answer
46 views
Simple pendulum and planet mass [closed]
A simple pendulum, $20cm$ in length, has the period of $2.7s$ on a certain planet. Find the mass of the planet if its diameter is $18000km$. $G=6.67\times10^{-11}Nm^2/kg^2 $
I have no idea how to get ...
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3answers
49 views
Forces involved in a climbing jet aircraft
I have a problem with which I need help. The question is:
A jet aircraft is climbing at an angle of 45° above the horizontal and is accelerating at 4.5m/s2. What is the total force that the cockpit ...
1
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4answers
62 views
Action Reaction when I pushing a trolley?
I tried to explain how those force work but I can hardly figure it out.
I exerted a force on the trolley and there will be a force on trolley on me as well. This is the newton's third law. But why the ...
0
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1answer
55 views
Bouncing ball simulation computer science
In my Computer science class I was given a problem where I have to simulate a bouncing ball using "real physics". I have been trying to find a equation that will simulate the height of the bounce ...
3
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1answer
31 views
Two masses on rope spinning around
Two balls of the same mass $m$ are connected to each other with rope
of length $l$. One of the balls is also connected to the ceiling with
a rope of the same length $l$. The balls are spinning ...
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2answers
81 views
acceleration due to gravity [closed]
From the picture we can evaluate the vertical and horizontal component:
Given on a book:
The figure above shows a small mass connected to a string, which is attached to a vertical post. If the ...
5
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0answers
68 views
Derivation of Universal Variables
Does anyone know of link to the derivation of the Universal Variables?
This is in regards to Kepler's equations. The Wikipedia link didn't have enough information for me, and the Colorado page ...
1
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1answer
69 views
A block, a string and Newton's third law
So this is a general force diagram of the system shown. My question is, according to the third law, if the block is exerting a force of magnitude mg on the thread in the down direction, then the ...
1
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0answers
19 views
Delivered/Reflected Power by Drive on a Hamiltonian System
Imagine a SHO with a drive F(t). (or in general a Hamiltonian system)
What is the power delivered to the system and can we talk about the power reflected? is i am imagining say a MW oscillator ...
-1
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0answers
24 views
how to dot product in 3 dimensions? [closed]
i have two vectors, vector A = 12 and vector C = 15 . vector A makes 60 degrees clock-wise x-axis. vector C makes 45 degrees clockwise z-axis, 30 degrees counter-clockwise y-axis. i did not ...
-7
votes
2answers
64 views
What is the sensation by man carrying a water bucker with an object floating in it? [closed]
A man is carrying a bucket with water. If a object is kept in it which floats in water, man will feel
1) heavier
2) lighter
3) none
I think when the body floats its weight is balanced by upthrust ...
3
votes
2answers
70 views
Extension to continuous in proofs of rigid body mechanics
I'm studying rigid body mechanics and I've seen several proofs of properties related to total angular momentum, kinetic energy, etc. that all regard discrete set of points. For example, to show that ...
7
votes
2answers
171 views
No closed orbits for a Newtonian gravitational field in 4 spatial dimensions
We are supposed to show that orbits in 4D are not closed.
Therefore I derived a Lagrangian in hyperspherical coordinates
$$L=\frac{m}{2}(\dot{r}^2+\sin^2(\gamma)(\sin^2(\theta)r^2 \dot{\phi}^2+r^2 ...
2
votes
3answers
99 views
How you feel in outer space vs. orbit?
I understand that when someone is in low earth orbit, the "pull" of their inertia is equal to the pull of gravity. However, the force of gravity is still acting on them. However, if they are in outer ...
3
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2answers
60 views
Frictional Forces
In the figure, blocks A and B have weights of 45 N and 23 N, respectively. (a) Determine the minimum weight of block C to keep A from sliding if μs between A and the table is 0.21. (b) Block C ...
3
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2answers
94 views
What is the physical significance of the off-diagonal moment of inertia matrix elements?
The tensor of moment of inertia contains six off-diagonal matrix elements, which vanishes if we choose the principle axis of the rotating rigid body and the components of the angular momentum vector ...
1
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2answers
66 views
Velocity of an object undergoing homogenous acceleration
So I was considering the following problem within the context of Special Relativity:
Given an object O, with initial velocity v, undergoing constant acceleration at a rate of a, I want to express the ...
45
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8answers
5k views
Proof that the Earth rotates?
What is the proof, without leaving the Earth, and involving only basic physics, that the earth rotates around its axis?
By basic physics I mean the physics that the early physicists must've used to ...
