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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2answers
65 views

Nature of tension in a massless rope [duplicate]

I'm faced with a conceptual problem, where I am supposed to describe the motions of the following system (two masses on each end of a totally inelastic rope hanged on a pulley): I understand that ...
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1answer
22 views

Torque in a 2-segment robot leg

I have a (hypothetical) robot with two legs, each with 2 segments, with a joint at the body of the robot and in the 'knee' of each leg, as in this (poorly-drawn) diagram: (Sorry about the quality and ...
0
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2answers
49 views

Calculate average speed of projectile with air resistance

There's a project that I'm working on that been bugging me for awhile. The project involves this senario: A projectile is released at 1000 feet per second and moves in a straight line infinitely ...
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3answers
36 views

Can a piezo actuator have infinite resolution?

See here: http://www.omega.com/googlebase/product.html?pn=LD400-1&gclid=CjwKEAjw77OhBRCJ7Onfp_HNtwYSJACZqHAWVTfW1BO4RSfSVjz9P3Q4FoPTvZ2r3NIc2W1uEthVhBoCgUHw_wcB I don't think so. Do they just ...
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0answers
30 views

Free body diagram of mechanisms

The image below shows a mechanism with 2 pin joints. On one of the pin joints, there is a torsional spring that exerts a torque $M_s = \kappa \theta$ (rest state is at $\theta = 0$). A force $F$ is ...
2
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1answer
32 views

Weighing with One-Foot Scale

I stand with left foot on a scale and the other on a piece of effectively incompressible material at the same initial height at the scale's top surface. The weight shown is WL. I repeat with right ...
2
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3answers
86 views

Unstable equilibrium in a pendulum

Consider a pendulum with a bob and a massless, rigid, hinged rod attached to the bob. The bob is at rest at the bottom most position. Neglecting friction, is it possible to impart such a velocity ...
2
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1answer
81 views

Confusion with Newton's Second Law : Position & Time Dependence of Force

For a conservative force $\vec{F}(x,y)$ we have $$\vec{F}(x,y) = - \vec{\nabla}\phi(x,y)$$ where $\phi(x,y)$ is a potential function for $\vec{F}(x,y)$. Again, Newton's second law states that $$ ...
3
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1answer
119 views

What is the physical interpretation of the linear coefficient in this ODE for projectile motion?

For the second order ODE governing the position of a projectile subject to air resistance $$ m\frac{d^2x}{dt^2} +k\frac{dx}{dt}+mg=0 \quad k>0, \> x(0)=0, \> x'(0)=V>0 $$ a ...
0
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1answer
55 views

Why does a Ball bounce back if Forces are Equal and Opposite?

When a ball is thrown onto a wall, the ball exerts a force onto the wall. According to Newton's Third Law, the wall will exert an equal and opposite force to the ball. Thus, how would the ball be able ...
2
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1answer
39 views

Beads flying out of flask

There is a popular youtube video of some metal beads being thrown out of a flask, literally hovering out of the container My question is how detailed a physical explanation of this phenomenon we ...
2
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1answer
83 views

Can't understand the meaning of a formula describing a stable equilibrium?

I've found this formula in a book and I can't understand its meaning: $$\frac{df}{dx}\biggr|_{x_0} < 0$$ It describes the condition of an object to being in a $\textit{stable}$ equilibrium. At ...
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1answer
36 views

Centripetal force in loop motion

I saw it from the book which talk about centripetal force in circular motion The main idea here is the balance in the term of relation between velocity and centripetal acceleration - centripetal ...
0
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1answer
59 views

Drag force on a flat plate

The solution for this apparently is $\frac{1}{2}C \rho A V^{2}$ where $C$ is the drag coefficient, $A$ is the area and $\rho$ and $V$ are the wind density and velocity. Let's do it without the drag ...
1
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1answer
49 views

Fictitious forces and $\omega$

I have been studying fictitious forces, such as the centrifugal force and Coriolis force. The equation for the centrifugal force is given by: $$F_{centrifugal}=-m\omega\times(\omega\times r)$$ My ...
4
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2answers
119 views

Newton's Third Law Exceptions?

Lately I've been brushing up on some of my old Physics texts from college. Most recently, I've been rereading parts of "Classical Dynamics of Particles and Systems (5th ed.)" by Thornton and Marion. ...
5
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2answers
874 views

Why do rockets jettison fuel tanks? [duplicate]

I'm trying to understand why rockets have multistages releasing their fuel tanks. Say a rocket $R$ has two fuel tanks $A$ and $B$, which respectively have masses $m_a$ and $m_b$, and the mass of the ...
0
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2answers
94 views

Why do we use less fuel by driving at constant speed?

It is common practice to drive at constant speed as much as possible to reduce fuel consumption, or at least to avoid "pumping" on the throttle (at frequencies high enough that the lowpass filter does ...
2
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3answers
168 views

Joules to do something

If my very limited understanding is correct, then, not accounting for gravity: 1 Newton can move 1 kilogram 1m But, can 2 Newtons move 1 kilogram 2 meters? Is this because 1 Newton = acceleration ...
2
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0answers
27 views

What will be the time taken by a stone to reach the ground if it is thrown with velocity $v$? [closed]

I was studying from my reference book and I got this question. I tried solving it by finding the total distance n average velocity but it didn't work please help me out.
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2answers
90 views

Why can a ball tossed up object free fall upwards?

I've found many websites that say that a ball tossed upward would be free falling upwards, but none of them say why. If the definition of free fall is an object that is falling while only under the ...
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0answers
31 views

Could an object higher than the stationary orbit be returned to the outgoing point on this orbit?

In the question Centrifuge speed of an object higher than a stationary orbit, I asked: Does an object higher than the stationary orbit move slower or faster around the world than the top of a tower ...
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2answers
53 views

Centrifuge speed of an object higher than a stationary orbit

In the question At what altitude above equator do gravitational and centrifugal forces cancel each other?, I asked how high a tower on the equator has to be such that at its top, gravitational and ...
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0answers
20 views

To find angular speed of a rotating body [duplicate]

A body moving with uniform angular acceleration covers 100 pi (rad)in first 5 s. Its angular speed at the end of 5 s (in rad/s) is?? My ans is 40 pi, but according to the answer given in my book ...
2
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2answers
51 views

Does the distance two weights are from you alter the difficulty of lifting them?

If I am weightlifting and I choose to do the deadlift, does it matter how far away from me the weights are on the bar, given that they are equally distance from me on both sides. E.g. I am deadlifting ...
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4answers
4k views

Why doesn't a tied balloon behave like a pendulum?

It is well known that a tied weight will oscilate under the effect of gravity if left from aside, like a pendulum. However, if we tie a helium balloon to the ground from and left it form the floor ...
2
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2answers
61 views

Question relating to energy transfer in between two particles

How would I go about calculating the maximum kinetic energy transferred from one particle when it forms an elastic collision with another particle. For example, if I had two billiards one with mass m ...
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2answers
78 views

At what altitude above equator do gravitational and centrifugal forces cancel each other? [closed]

How high has to be a tower at equator to get on its peak the same - but of course inverted sing - value of gravitational and centrifugal forces?
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2answers
70 views

Change of kinetic energy in a two particle collision

A problem I am working on proceeds as follows: A billiard ball of mass $M$ is initially at rest on a horizontal frictionless table. Another ball of mass $m < M$ and velocity $\mathbf{v}$ in ...
6
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1answer
408 views

Impact force in a fall

I'm a climber and I constructed myself an anchor that I fixed to a rock wall. To test it, I hooked to it a 12mm in section steel cable with a length of 2,8m and a concrete block of 30kg to the other ...
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0answers
72 views

Lagrangian mechanics is different form Newtonian? [duplicate]

I am a post graduate student and had completed my classical Mechanics with Newtonian mechanics to Hamiltonian mechanics. I have better understanding of Newtonian, Lagrangian and Hamiltonian. But I ...
0
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2answers
134 views

7 Billion people jumping at once

What would happen if every person in the world gathered at a minimum possible area and jumped all at once? Would that have any effect on earth?
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2answers
30 views

Cylinder falling down the edge of a table [closed]

Suppose, a cylinder is placed on its lateral side at the edge of a table, carefully, so that the slightest push makes it fall from the table. We give it a gentle push. And it begins to fall. How is ...
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3answers
86 views

Distinction between torque and force

Distinction between Torque and Force. Consider a case when a cylinder is rolling down a rough inclined plane. While analysing its motion, we consider the force applied by the friction and the ...
1
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1answer
33 views

Accelerated wedge [closed]

Consider the following figure, where a mass $m$ is placed on a wedge which is accelerated to the right ($\vec a$) which could be negative. The coefficient of friction between the mass and the wedge ...
1
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3answers
77 views

Direction of friction force between two boxes

There are two boxes on top of each other. The bottom box is dragged right by a constant force. What is the direction of friction of the top box against the bottom box?
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0answers
40 views

At time $t=0$, what are the magnitude and direction of the perpendicular component of dp/dt? [closed]

In the dark in outer space, you observe a glowing ball of known mass 4.6 kg moving in the xy plane at constant speed in a circle of radius 7 m, with the center of the circle at the origin (< 0, 0, ...
4
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2answers
170 views

Is a chain REALLY only as strong as its weakest link

I heard this quote a lot (especially from my teachers) and I always wanted to know whether or not it was actually true. I think that its partially true; a chain with one weak link is weaker than a ...
1
vote
1answer
67 views

Tangential acceleration [duplicate]

If you are spinning an object using a mass-less string with constant speed in a vertical circle, and when the object is at an angle with the vertical, what happens to the component of weight in the ...
1
vote
0answers
60 views

Tension problem for rotating object? [closed]

when an object (tied to a massless string) is moving in a vertical circle with constant speed, does it have tangential acceleration when it is at some angle (theta) from the vertical? I am assuming ...
3
votes
2answers
75 views

Ball Bearing Inside a Hollow, Spinning Rod: where is the logical flaw?

As described in the title, suppose we have a frictionless, hollow rod that is rotating in the $xy$-plane with some fixed angular velocity $\omega$. The rod is pivoting around its midpoint. Suppose we ...
1
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1answer
43 views

A shorter impulse-contact period than a rod´s mechanical longitudinal wave propagation period may fail to accelerate the rod?

I have viewed and read several papers related to this subject but cant find any help to understand some seemingly a simple and a straitforward point, about whether a short impulse period compared ...
1
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0answers
27 views

Which force is necessary for providing centripetal force to a rotating gyroscope?

When a gyroscope is precessing around an axis due to a certain applied torque, if we look at the center of mass , it is going around in circular motion. So there must be some force which provides the ...
3
votes
1answer
59 views

Moments of vibrating string

I have to calculate first 10 moments for vibrating string with damping, but I don't know how to do it. I read about moments and in definition they mention linear system $$x'=Ax+Bu, \qquad y=Cx$$ with ...
3
votes
5answers
256 views

Why doesn't this perpetual motion machine work?

Imagine a non-magnetic tube bent into the shape of a triangle, with two sides forming downhill ramps, and the third side connecting the two ramps. Through this tube travels a metal ball, which is ...
0
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1answer
77 views

Does Newton's first law apply also to non-newtonian physics?

I think I understand than an example of Newton's first law (intertial frames) would be a single asteroid in vaccum with no other bodies around, a comet in such free space or likewise. Then I think the ...
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1answer
50 views

An alternate approach to find variation of gravitational acceleration with respect to depth of an object in Earth

As we go down the Earth, assuming it to be a uniform sphere abiding only to Newtonian physics, the gravitational acceleration imparted to an object by the Earth goes on decreasing, and decreases to 0 ...
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2answers
42 views

The effect of windspeed on a car

I've worked problems in the past in trig class concerning the effect of wind on the speed of a plane and it's flight path and was wondering if a similar thing occurs with a car. First off, I'm ...
1
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0answers
15 views

If a nozzle that converges from an inside diameter of 5cm to 3.5cm carries a gas at a VFR of 0.10 m^3/s, what is the change in average velocity? [closed]

If a circular nozzle that converges from an inside diameter of 5 cm to 3.5 cm carries a gas at a volume flow rate of $0.10 m^3/s$, what is the change in average velocity of the gas? (A nozzle being a ...
1
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1answer
48 views

Modeling wall's behaviour

Sorry if the quesiton is inconvenient, but I judged the physics forum would be the best place to go. My house is divided in two parts by a wall, and there's some tree pushing it, so the wall is about ...