Questions tagged [newtonian-mechanics]

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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How do balances (not scales) work? [duplicate]

More specifically, why does having two objects of different weights make the balance lean to one or the other then stop partway? Why does the balance not just keep tilting until it falls to the side? ...
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Conditions for using the work-energy theorem

Suppose I let a block fall from a height above a vertical spring. Any air drag is ignored. I want to find the maximum compression the spring will undergo. Is it possible to use the work-energy theorem ...
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How is the curvature term of the Friedmann Equation calculated with the Newtonian derivation?

I'm trying to develop and intuitive understanding of the Friedmann equation. I'm afraid I get lost with the relativistic derivation as it's just a lot of crank-turning. When I derive it from the ...
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4answers
56 views

Work Equals Torque? Horsepower, Pulleys

While reading one definition of torque, I saw its units are Newton-meter, which is the same as work. But sources usually make it a point to emphasize "even though both work and torque units are ...
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Is conservation of angular momentum responsible for rotating a rigid body when it slows down an internal wheel?

Suppose that there is a rigid body, such as a satellite, which contains inside it a wheel that is spinning at a constant rate. This means that the satellite has a certain, constant, angular momentum ...
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49 views

How to understand pseudo forces in the Lagrangian formalism?

Consider a free particle in a rotating reference frame. Let us say the coordinates of the particle are given by $(x',y')$ in this frame. For an observer on this frame, (I suspect) the Lagrangian is ...
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Angular Momentum about an arbitrary point same as centre of mass?

The angular momentum of an object about an arbitrary point $O$ is given by, $$ \mathbf{H_O}=[I_O]\mathbf{\omega}$$ where $[I_O]$ is the moment of inertia tensor about $O$. And for the center of mass $...
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1answer
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Stacked bodies, no applied forces, internal forces accelerate the whole system [closed]

A block P of mass $m_{1}$ in on a frictionless horizontal plane and a block Q of mass $m_{2}$ is always on top of P. Initially P and Q are at rest. At time t=0, an initial speed $v_{0}$ is given to P ...
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Infinite rotating discs

Consider the given arrangement of infinite uniform discs$A_1,A_2,A_3,...,A_n$, each of mass m and radius R. Each disc is kept on a stair. Height of each stair is R. Strings are wrapped around discs ...
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Model (or approximate model) of drone take-off forces?

I would like to implement a model of the force/uplift the floor makes in a multicopter take-off, but I don't find any info of this exact dynamic. Is there any paper that tackles this issue? Or any ...
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Net Force on a System [closed]

In the figure given below is a system of a mass M ,a pulley and 2 masses of mass m. Now there is friction between bodies A and C and B and C. A force ($ F$) is applied in such a way that body C is a ...
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Will a stiffer stretched spring or compressed spring exert a greater elastic spring force? [closed]

When the same load is added onto the spring, for example, spring P is stiffer than spring Q. Then which would exert a greater elastic spring force on the object?
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Tension required for perfectly horizontal rope (having some mass per unit) [closed]

What is the tension required for a rope with a finite mass per unit length, hanging between two fixed equal altitude points under gravity, so that the rope is perfectly horizontal (without any "...
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1answer
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The shell theorem and divergence in Susskind's GR lecture

In the lecture available here, at around 1:36:50, Susskind seems to argue that you can derive the fact that the gravitational field inside a spherical shell (of constant density) is 0 from the ...
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2answers
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Condition for force acting on a particle for it to move in a hyperbola

Consider 2D motion of a particle, For a particle to move in a circle there must be a force of constant magnitude acting on it always pointing towards the centre of the circle. Similarly for an ellipse ...
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Estimating the displacement/force of a string (eg. guitar, piano) being struck by a mass (eg. by hammer or plectrum) at a given initial velocity

I have created a string audio synthesizer (eg. guitar, piano) based on physical modeling. It incorporates modeling for all the major phenomena that characterize a string. This includes things like ...
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How will a body stretch under the action of unbalanced forces, F1and F2 say, where F2>F1? [closed]

Suppose I have a rope made of slime or any other flexible material. Now what I will do is pull one end of the rope with a force F1 and the other end with a force F2, F2>F1. Now as usual the rope ...
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Work and Energy question, using Tension

Given this image, $2$ objects are connected via a spring (its mass is negligible) The spring constant is $k$ and that is all that is given.. mass of $A$ is just $m_A$ etc.. and $g \approx 9.8 \frac{m}{...
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1answer
39 views

Does it take more energy to move directly against gravity than to move laterally? [closed]

Person A is holding a 1 kg object. He lifts it upwards (against gravity) by one meter. Person B is holding a 1 kg object. He move it by one meter horizontally, at a 90 degree angle of the force of ...
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27 views

Physics pendulum problems [closed]

Mr A has a bucket of water suspended from a fixed point by a rope.Mr A set the bucket in such a motion that the system swings like a pendulum. But the bucket leaks and the water slowly flows out of ...
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Momentum of An Object [closed]

If four horizontal forces F1=3N F2=6N F3=3N AND F4=6N is applied on a body of mass 5 kg. If force F3 is removed ,then find the value of rate of change of momentum
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On Validity of the formula for gravitational potential energy

The formula for gravitational potential energy, $$-G\frac{m_1 m_2}{R},$$ is found by using the fact that the change in potential energy is equal to negative of the work done ( by conservative forces). ...
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A fighter jet making a vertical circular motion [closed]

A fighter jet making a vertical circular motion with radius of 3 km at speed of 230 m's. If the mass of the pilot is 60 kg, find the normal force on the pilot at the top and lowest point.
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Why is the kinetic energy of this particle of mass $m$ zero at the bottom point? [closed]

Why is the final kinetic energy of the particle of mass m zero.It should have some velocity when it reaches the bottom?? Can we solve this solve by using the concept of reduced mass system?
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2answers
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Finding acceleration of center of mass in cart pole problem

In this link about finding equations of motion of cart pole problem, There is an equation about acceleration of center of mass of the pole. Screenshots of them below. I don't understand why they have ...
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1answer
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Understanding potential energy (2)

I know that several questions on this topic and one with even the same name exists, but I don't think they fully answer my questions. I request you to first hear me out, and then point out any ...
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1answer
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Friction on a wire (angle of repose) [closed]

A wire is molded into a shape in vertical plane as shown. The equation is given by $y=0.5\sin 2x$. A bead B can slide on the wire.The coefficient of friction between bead B and wire is $0.5$. The ...
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Cart Pendulum Problem [closed]

The second image shows the speed profile of the cart as well as the sway angle of the pendulum. The length of the pendulum is fixed at 30m, for the above image. Is it possible for the sway angle to be ...
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2answers
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What happens in Newtonian mechanics when a particle reaches infinite force position?

Suppose a particle of negligible mass is placed at e.g. $x=1$ inside a one dimensional space with a force field generated by the gravitational attraction of a point mass at the origin $0$. I.e. the ...
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1answer
37 views

How to identify internal and external forces acting on a system of particles?

In my Physics textbook there is sample problem in which a firecracker placed inside a coconut of mass M, initially at rest on a frictionless floor, blows the coconut into three pieces (A, B and C) ...
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1answer
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Quantities that are functions of velocity [closed]

Let's think about the following quantities: Kinetic energy: $K=\frac{1}{2}mv^2$ Lorentz's Force: $\vec{F}=q\vec{E}+q\vec{v} \times \vec{B}$ This two quantities are not invariant under Galilean ...
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If an body has zero acceleration,and friction force is applied on that body does that body have net force Ffriction?

Imagine a body with force $F$body and friction force as $F$friction(Friction force is not zero). When body goes with zero acceleration(no change in speed) $a$object = 0 the net force equation states ...
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Why do tidal waves appear suddenly in some rivers?

As tide approaches in lower part of some rivers (e.g. Ganges), a several feet high tidal wave enters from the sea against the flow of the river (making a great noise), and the water level suddenly ...
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2answers
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Changing length of Pendulum

Let's say we have a pendulum and with an initial displacement of 5 degrees, it starts oscillating. Assuming ideal conditions, the pendulum will oscillate forever with its maximum sway angle being 5 ...
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1answer
31 views

Torque and inverted pendulum

I'm supposed to derive a relationship in which the change in gravity $\delta g$ is linked to the change in length of the spring $\delta s$. When the beam is tilted due to increased weight or gravity, ...
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1answer
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Equations of motion for a spring attached to a parabola [closed]

I have to find the equations of motion for a system formed by a mass $m$ whose movement is fixed to the parabola $y = ax^2$, $a > 0$. Attached to this mass, there is also a vertical spring with ...
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3answers
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Why does driving a screw in spurts work better?

When you drive screws into wood with a driver or drill, it is often the case that mid-way through the process the screw will suddenly bind and eject your bit (assuming it's not a Robertson or Torx). ...
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Collision of constrained spheres

In a standard collision of two spheres, if one wants to be general for inelastic, rough rotating spheres, there are two coefficients of restitution used. The coefficient of restitution in the normal ...
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2answers
73 views

Work-energy theorem and the frictional force

During my attempt of fully grasping the work energy theorem, I came across this written in my textbook: The frictional force, which we represented as a constant force is in reality quite complicated, ...
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2answers
46 views

Problem with friction in circular motion [closed]

I can't seem to understand what would be the direction of friction in the case of uniform and non-uniform circular motion. Can someone please help?
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1answer
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Why center of mass is at the focus for elliptical orbits?

I know there are similar questions with answers like this one in physics stackexchange but before I read these I had a completely different argument with a different conclusion which I thought was ...
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Push up question in physics [closed]

how can I calculate F3 when the mass is 69 kg
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Projectile motion:How are we gonna do this? [closed]

particle from ground passes two points which are heights h1=12m h2=18m above the ground and a distance d=10m apart. what would be the minimum speed of projection.(g=10m/s2) I got that we can resolve ...
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1answer
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I am confused about resolving of forces in a certain situation. Where am I wrong?

I was solving questions related to circular motion of a pendulum hanging from a ceiling in an inertial frame having angular displacement $θ$ and if I resolve Tension into vertical and horizontal ...
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1answer
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How much energy is stored in a evacuated tube?

So in this video they have an evacuated tube with a golfball at one end, they quickly open one end and the golf ball shoots out the other, hitting a target. Resulting in a rapid unplanned disassembly ...
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1answer
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Meaning of effective mass in a spring

In real life we don't have ideal spring so when doing experiments we need to take in our calculation the mass of the spring it self (the effective mass) wich made me doubt about the physical meaning ...
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1answer
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How does shear-stress act on a spring hanging vertically with a mass attached to its end?

I have come to known that both longitudinal and shear strain act on a spring when it is hanging. I can understand how longitudinal strain acts but I do not understand why shear stress/strain can act ...
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1answer
56 views

Gravitation: Collision of a satellite and Meteorite [closed]

A satellite is orbiting around a planet in a circular path of radius $R$. A meteorite of mass $m$ collides with the satellite and sticks to the satellite. After collision, the satellite is seen to ...
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4answers
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Which force is doing the work here?

My text book (Fundamentals of Physics by Halliday, Resnick, and Walker) mentions the following about the work done in internal energy transfers: An initially stationary ice-skater pushes away from a ...
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Equilibrium Reaction Forces on an Inclined Rod

Suppose we have a uniform steel rod leaning against a friction less wall in static equilibrium. Frictional force between the lower end and the floor is less than its limiting value by a finite amount. ...

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