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.

learn more… | top users | synonyms (3)

0
votes
2answers
124 views

How can I find the height for a looping pendulum? [closed]

I have a ball attached to a string, hanging on a rod placed $L$ meters above the floor. I release the ball and string at a 90 degree angle and let it loop around another horizontal bar after it ...
0
votes
1answer
37 views

Toppling and Torque related to it

When a body is said to be being just about to topple about one of its edge due to a force F applied, why do we not consider the torque of normal about the edge point but about the centre of mass? Are ...
0
votes
0answers
9 views

What is the analytical approach for a fiber cutting machine?

Folks, so today in the Lab I came up with this problem (see picture). It shows a cross section of a cutting machine. There's a blade moving with a constant speed dx/dt towards the center of the roll ...
0
votes
2answers
101 views

A question about the famous bucket experiment

Suppose that we have a bucket containing two liquids with different densities.Suppose also that i connect the bucket with an electric motor and i rotate the bucket. Why when the bucket rotates, the ...
1
vote
2answers
121 views

Difference between potential centrifugal energy and rotational/kinetic energy

I'm having troubles to understand the difference between kinetic energy and potential centrifugal energy in some situations. I make an example where I am confused. A object moves on a rod attached ...
0
votes
2answers
47 views

Problem with variation of velocity, doubt on the work energy theorem

I think I did not understand the use of the work energy theorem. Here is a situation I am confused about. Consider an object moving in the $xy$ plane with a constant velocity $\vec{v_0}$ at an angle $...
1
vote
2answers
303 views

Why does something on an inclined plane move forward at all?

We just started studying about the inclined plane and vectors in motion, but i don't understand one thing: Why on earth does the object on the inclined plane move forward (I.e in the direction where ...
0
votes
1answer
98 views

Rocket equation derivation mistake by my professor

In one of my lectures our physics professor gave a derivation of the ideal rocket equation as follows: Let $v_G > 0$ be the velocity at which the gas is emitted from the rocket. Let $m$ and $v$ be ...
1
vote
2answers
68 views

Free falling and bouncing back

My confusion arises with free falling body. For a free falling body the displacement ~ time graph has a kink (at the time when the body hit the ground ). at a kink point, a function is not ...
0
votes
2answers
193 views

Elastic collisions and 90 degrees angles [closed]

Why is it that if the angle between the two objects that collided together is 90 degrees then it must be perfectly elastic? Is there any theoretical proof other than convention?
1
vote
1answer
46 views

Note and homework organization [closed]

I am currently in a mechanics class and have some trouble trying to figure out how I should structure my lecture notes and my homework. I recently began rewriting my notes after class but I am still ...
0
votes
0answers
47 views

About the formula of pendulum simple

for the modulation and the simulation of a pendulum simple , I'm Find this formula : a(t) = a0 * sin ( sqrt(g/l) * t * Pi/2 ) - [ k/(mll) * cos ( sqrt(g/l) * t * Pi/2 ) * t ) ] ...
3
votes
2answers
150 views

Effect of friction on a moving body under a variable force

Given the system in the figure: The block slides on a horizontal surface and is acted upon by a force $P$ which varies in magnitude as shown. Knowing that the coefficients of friction between the ...
0
votes
2answers
113 views

Why can't we put an object anywhere in the earth's orbit around the sun instead of Lagrangian points?

If we place an object in the earth's orbit around the sun, it should have the same orbital period right? For example, what would be the behavior of an object in orbit at point A1? It is at the ...
0
votes
1answer
60 views

How does paddling in the water help a boat move forward?

The way I've seen it explained is like this: it all has to do with Newton's third law. However, the "equal and opposite" reaction predicted by the third law acts on the paddle - which is not ...
0
votes
0answers
32 views

What is the equation for the position of a falling body as a function of time? [duplicate]

I know that near the surface of the earth a projectile's position follows a parabolic curve in function of time because the acceleration is constant (about 9.8 m/s2). However, acceleration ...
1
vote
4answers
94 views

Would running along Earth's Surface at escape velocity cause you to get out of the Earth's gravitational pull? [duplicate]

If one were to run/drive/fly along the earth's surface (by this I mean tangential to the Earth) at escape velocity (about 7 miles per second), would that person escape the gravitational pull? If not, ...
0
votes
1answer
55 views

If a disc is rolling on a surface, how do you verify that no slip occurs? [closed]

If I have the values for the coefficient of static friction (0.1) and all the other variables, how do I verify that no slip occurs?
1
vote
1answer
80 views

How does friction affect the motion of a pendulum?

I would like to know what is the difference in the equation of motion of a pendulum in the presence or the absence of frictional forces. And how this translates to the solution of those equations?
0
votes
3answers
51 views

what is the difference between these two systems? [closed]

what is the difference between these two pulley systems when calculating the angular acceleration if the moment of inertia and radius is the same?
0
votes
1answer
52 views

Does the rotational form of Newton's second law always hold?

Does the equation, $$\vec \tau=I\vec \alpha$$ (rotational form of the second law) always hold? If not, in what conditions does it hold true?
0
votes
0answers
52 views

Rotating rigid rod in empty space [duplicate]

To begin, we assume there is a rigid rod in empty space which has no rotation with respect to the fixed stars. The frame of the rod is now an inertial reference frame, say $F$. 1) The rod now has a ...
1
vote
1answer
44 views

Dependence of tension (considering a pulley system) on the mass of loads

Consider the diagram below All circles are pulleys, which are fixed at the ceiling. M represents an engine (with a certain power) that is pulling the cable. C and D are weights. The acceleration of ...
1
vote
1answer
76 views

A cruise ship bumping against a lock gate [closed]

For my project, I need to create a lock gate which will be used for the Panama Canal. One of the many thing my teacher said, was that for the design of the lock gate, the gate should not fail when it ...
0
votes
1answer
66 views

How do I show that the total energy of a particle moving in an electrostatic field is constant?

Basically the Lorentz force says that: $$F=qE+qv × B$$ I am asked to show that if a particle moves in an electrostatic field $$E= - ∇V(x,y,z)$$ and ANY magnetic field, then the energy: $$\frac{1}{...
0
votes
0answers
38 views

Does frequency of a vibration wave of a cantilever depend on its deflection?

cantilever= a beam fixed at one end only deflection is the initial displacement of the free end. the beam is let go when the free end reached its position it will vibrate, does the frequency of ...
1
vote
0answers
24 views

Standing waves arbitary frequency

Suppose I have a string that is fixed rigidly at one end. Now when I start making wave, it will get reflected and should lead to standing waves (Mathematically and by visualization), but then we have ...
1
vote
1answer
97 views

Oscillation of non-uniform plank on parallel springs

A plank of length $l$ and mass $m$ is placed on two parallel springs, each with spring constant $k$ and equidistant from the plank's horizontal center of gravity. When the plank is displaced from it's ...
1
vote
0answers
13 views

Power Generation Via 2 connected objects below distinct orbits

As an example: Large weight A sits just below Earth's orbit Large weight B sits just below Moon's orbit A, B are connected by sufficiently strong material (may not exist, and if so how much ...
2
votes
4answers
213 views

Why does Torque exist?

Specifically, why does force increase with the moment arm? What about making a perpendicular force farther away from the axis of rotation increases it? How does the moment arm cause that?
1
vote
4answers
216 views

Is it correct to say Newtonian mechanics is a subset of Quantum mechanics?

I grew up in a three dimensional (3D) reality described quite well by Newtonian mechanics as opposed to the reality described by Quantum mechanics. That is I could go to bed at night without worrying ...
1
vote
2answers
47 views

Simple harmonic motion..direction of acceleration

To solve questions about simple harmonic motion, my book says $\ddot{x}$ (i.e. acceleration) is in the direction of increasing $x$, i.e. away from equilibrium. I don't understand why is this so, since ...
5
votes
1answer
94 views

What's the distance between the center of mass and geometrical center of Earth? [closed]

With a good approach we can say that they are identical. But how accurate is this approach? Since Earth is not homogeneous there must be (can be) some difference. In other words I'm asking if Earth ...
2
votes
4answers
272 views

Rate at which a pendulum bob slows due to air resistance?

I know that "perfect" pendulums would be able to swing forever, unperturbed by air resistance. However, since there is air resistance around us, pendulums (swinging bobs) slow down and move closer and ...
36
votes
4answers
1k views

Is there an underlying physical reason why the Coriolis force is similar to the magnetic component of the Lorentz force?

I couldn't help but notice that the expression for the magnetic component of the Lorentz force, $$\mathbf F = q\,\mathbf v \times \mathbf B\,,$$ is very similar in its mathematical form to the ...
0
votes
2answers
128 views

Why is this specific definition of acceleration used in deriving a general equation for kinetic energy?

$$\sum_{i=0}^n m_i v_i$$ as well as $$\frac{1}{2}\sum_{i=1}^n m_i v^2_i$$ Have been proved to be conserved by Newton & Leibniz, respectively. (http://en.wikipedia.org/wiki/Vis_viva) I don't ...
0
votes
1answer
98 views

Sliding blocks problem

My first post here, so I apologize if this is duplicated elsewhere. It IS a "homework" problem, but it's public domain, a posted exam with answers... http://www.mun.ca/physics/undergraduates/...
0
votes
1answer
83 views

Period of simple pendulum accelerated horizontally

I'm confused about simple pendulum problems where the pendulum is accelerated horizontally of anyway not vertically with acceleration $\vec{A}$. $m\vec{g} + \vec{T}-m \vec{A} =m \vec{a}$ So $\...
11
votes
2answers
2k views

Throwing a Football. Is it truly parabolic?

Driving into work, I started thinking about the arc of something being thrown and was puzzled about how gravity's affect is squared per second for falling bodies. Intuitively that implies the shape ...
1
vote
2answers
115 views

Forces on wheels in an accelerating vehicle

Assume that a motorcycle of mass $m$ has two wheels that are equidistant from its centre i.e the force on each wheel is $mg/2$. If the motorcycle accelerates forward, will the two forces on each ...
0
votes
1answer
92 views

Fallacious derivation of the rocket equation

Consider a rocket in free space of initial mass (including fuel) of $m_0$ using up/ejecting fuel at a constant rate $r$ (mass per time). That means that at time $t$ the rocket has mass $m=m_0-rt$. The ...
2
votes
7answers
413 views

Why is force a vector? (The Feynman Lectures)

A vector is a quantity that transforms just the way the coordinates transform under rotation (while a scalar remains invariant under rotation). In FLP, he says suppose $F$ is a vector and probably ...
3
votes
1answer
116 views

Effect of general relativity on Newton's second law

Let's say I have some object, like a long pole, that is 30 km long with non-zero mass $m$. One end is resting on the Earth's surface and it is sticking straight up, perpendicular to the surface. ...
6
votes
1answer
151 views

Derivations of Newton's laws?

I feel convinced that the mathematics behind newtons laws can be derived from Noether's symmetry theorems. The fact that displacement s can be described by a cartesian coordinate system with a ...
4
votes
1answer
85 views

Cylinder on an accelerated rough plane [duplicate]

The following figure shows a cylinder resting on a rough horizontal rug that is pulled out from under it with acceleration $a$ perpendicular to the axis of the cylinder. What is the motion of the ...
0
votes
2answers
58 views

How can amplitudes be treated as vectors in Simple Harmonic motion?

The amplitudes of 2 SHM are scalors. When we combine the two SHM eq.(lying along the same line), the resultant expression becomes of amplitudes treated as vectors and the phase angle between them as ...
2
votes
1answer
65 views

Moment of Inertia of Square Lamina [closed]

I know how to compute this using an integral. However, I was told that I could derive this as well by placing 4 squares together of moment of inertia $$I=kmr^2$$ and derive it again but I'm not sure ...
3
votes
1answer
37 views

Solving an acrobat problem in 3 methods

A circus acrobat of mass $M$ leaps straight up with initial velocity $v_{0}$ from a trampoline. As he rises up, he takes a trained monkey of mass $m$ off a perch at a height $h$ above the trampoline. ...
0
votes
2answers
98 views

What formula do I use to calculate the force of impact of a falling object?

I am trying to calculate the force of impact of a falling object. I did my egg drop project. I dropped the egg from 10m with a mass of 126kg and with the velocity of 14.1 m/s. Which formula should I ...
1
vote
1answer
79 views

How can the work done by friction be positive? [closed]

I have this energy related problem that i cannot understand in this problem, I am required to find the velocity of the 4.8kg mass when it hits the ground. I easily solved this problem using newton's ...