# Tagged Questions

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 determine the equation of motion of slinky?

I'm trying to analyze the forces exerted to slinky. First, I've divided both ends. The red vector is the force exerted by slinky itself, and the green vector is gravitational force. Force exerted ...
1answer
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### Problem with a rotating frame of reference on the South pole

Consider this problem: A high-speed train is traveling at a constant 150 m/s (about 300 mph) on a straight horizontal track across the south pole. Find the angle between a plumb line suspended ...
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### How can a car's engine move the car?

Newton's First Law of Motion states that an object at rest or uniform motion tends to stay in that state of motion unless an unbalanced, external force acts on it. Say if I were in a car and I push ...
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### Friction on a conveyor belt

I was surfing through an Olympiad paper and I was caught with this question- A block of mass 1 kg is stationary with respect to a conveyor belt that is accelerating with $1\, \tfrac{m}{s^2}$ ...
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### How can I determine whether the mass of an object is evenly distributed?

How can I determine whether the mass of an object is evenly distributed without doing any permanent damage? Suppose I got all the typical lab equipment. I guess I can calculate its center of mass and ...
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### Effective mass in Spring-with-mass/mass system

Suppose you have a particle of mass $m$ fixed to a spring of mass $m_0$ that, in turn, is fixed to some wall. I'm trying to calculate the effective mass $m'$ that appears in the law of motion of the ...
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### Static friction force on a block in a tunnel

Linked to this Comparing Static Frictions Suppose there is a cuboidal vertical tunnel , and a cubical block in it such that all surface of the block are in contact with the four walls of the ...
1answer
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### If An Object Explodes With A Force, What Force Are Fragments Given?

So let's say for example I have an object with 5kg of mass. It explodes with a force of 500N. The object fragments into four fragments: a 0.5kg, a 1kg, a 1.5kg and a 2kg object. What force does ...
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### Vector cross product of $\mathbf{r}$ and $\ddot{\mathbf{r}}$ in polar coordinates

I'm struggling with the following question: Question 6 A planet of mass $m$ moves under the gravitational attraction of a central star of mass $M$. The equation of motion of the planet is ...
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### newton's laws - involving block and conveyor belt [closed]

i was surfing through a physics book when i encountered this problem- A block of mass 1 kg is stationary with respect to a conveyor belt that is accelerating with 1 m/s^2 upwards at an angle of ...
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### Lagrangian with a general constraint [closed]

Can any body help me out to solve this problem? I am familiar with mechanism of Lagrangian and I can solve some problems with constraints but this one is really hard to solve.
4answers
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### Is it possible to whirl a point mass (attacted to a string) around in a horizontal circular motion *above* my hand?

I'm studying circular motion and centripetal force in college currently and there is a very simple question but confuses me (our teacher doesn't know how to explain either :/), so I hope we can sort ...
1answer
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### A rod of length $L$ & mass $M$ is rotating in a circle about one end then calculate tension in the rod at a distance $x$ from the support

A rod of length L & mass M is rotating in a circle about one end then calculate tension in the rod at a distance 'x' from the support ? For its solution why should we take mass of L-x portion of ...
1answer
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### Another Inclined plane question

I did the FBD, and I found too many variables which are not eliminating...Moreover, I believe this question is based on kinetic and static friction. But, $\mu$ here is ambiguously defined...How Do I ...
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### The motion of a spring

I have a question about the force set by this spring, I saw many times that $\overrightarrow{F}=-Kx\overrightarrow{i}$. I'm asking why not using $\overrightarrow{F}=Kx\overrightarrow{i}$ without the ...
1answer
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### Comparing Static Frictions

In this figure, which of the static frictional forces will be more? My aim isn't to solve this particular problem but to learn how is static friction distributed . Since each of the rough-surfaces ...
3answers
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### Moment of Inertia (triangular plate)

I want to generalize the formula for the MOI of a triangular plate (sides $a,b,c$) about an axis passing through mid point of one sides and perpendicular to it's plane . The mass of plate $M$ is ...
2answers
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### Massless string Paradox

If we introduce the notion of a massless string to denote the fact that net force on a massless string will always be $0$, since it is massless . How can these massless strings ever accelerate when ...
1answer
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### Work done by Static friction

Here $v1$ is relative to the block on which sphere is pure rolling but static friction isn't $0$ as of now . In the following diagram, is work done by static friction $0$ ?, since the point of ...
1answer
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### Boundary conditions on wave equation

I am having trouble understanding the boundary conditions. From the solutions, the first is that $D_1(0, t) = D_2(0, t)$ because the rope can't break at the junction. The second is that ...
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### Potential energy sign conventions

Almost every book on physics that I read have some weird and non-clear explanations regarding the potential energy. Ok, I do understand that if we integrate a force over some path, we'll get a ...
2answers
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### Centripetal Force Acceleration

Suppose you want to perform a uniform circular motion . Then a body performing uniform circular motion horizontally needs an acceleration $= \frac{v^2}{r}$ at each point on the circular path with ...
1answer
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### Physics of the point of contact for a spinning top

I understand how spinning tops don't tip over, cf. e.g. this and this Phys.SE questions. What I'm more interested is in identifying the factors that determine the direction the spinning top moves to? ...
1answer
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### In tennis, why does topspin serve bounce higher than flat serve?

When receiving servers (while playing tennis), I've noticed that the tennis ball seems to bounce up higher on me when the server uses a topspin serve than when the server hits a flat serve. Why is ...
0answers
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### A slender rod with a ball at the end

A slender rod is attached to a block accelerating horizontally. The rod is free to rotate without friction. At the end of the rod is a ball. As the block accelerates, the slender rod will be deviated ...
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### Object on an inclined plane

I was solving a question about inclined planes, and it got me thinking: Imagine a scenario where, an object is on an inclined plane and the inclined plane is on a frictionless surface, and is itself ...
4answers
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### What do people actually mean by “rolling without slipping”?

I have never understood what's the meaning of the sentence "rolling without slipping". Let me explain. I'll give an example. Yesterday my mechanics professor introduced some concepts of rotational ...
1answer
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### How reliant is the Solar System on being exactly the way it is?

We know that all objects with mass exert forces on all other objects of mass such that $$F = \frac{GMm}{R^2}.$$ And as others have discussed the planets do interfere with each other ...
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### Tension in a closed loop around an object, carrying stuff

Sorry when this sounds like a first year physics homework question, but it's actually not. It arose during a discussion regarding safe practices for rock climbing anchors... So here we go: Imagine ...
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### What force does the seat exert on the rider at the top and bottom of the ride? [closed]

A 75 kg person rides a Ferris wheel which is rotating uniformly. The centripetal force acting on the person is 45 N. What force does the seat exert on the rider at the top and the bottom of the ride?
1answer
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### A theoretical problem on Mechanics [closed]

Two particles with masses $m_1$ and $m_2$ are moving in 3D space with some Cartesian coordinate system. There are known the laws of motion of these particles, i.e. the position vectors $\vec{r_1}(t)$ ...
1answer
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### Chain of balls on an inclined plane

Suppose we have some inclined plane, and there is some chain of balls of length $l$ and mass $m$ lying on it. No friction at all in the system. 1) What is $x_0$ (the vertical hanging part of the ...
1answer
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### Centripetal force and circular motion

I have a doubt, say when a body moves in a circular loop, there are basically two types of acceleration acting on the object. One is the linear acceleration which is basically tangent to the circle, ...
2answers
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### Why is potential energy negative when orbiting in a gravitational field?

I had to do a problem, and part of it was to find the mechanical energy of satellite orbiting around mars, and I had all of the information I needed. I thought the total mechanical energy would be the ...
1answer
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### Initial position and velocity of rocket to escape earth's gravity

I'm trying to numerically simulate a spacecraft trajectory between earth and mars. I already wrote the solar system model where the sun is at the origin of the x,y,z plane Earth and Mars are orbiting ...
5answers
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### Why Won't a Tight Cable Ever Be Fully Straight?

I posted this picture of someone on a zipline on Facebook. One of my friends saw it and asked this question, so he could try to calculate the speed at which someone on the zipline would be going ...
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### Work And Energy Question [closed]

$H = 3\text{ m}$,$m=2\text{ kg}$ The right side is rough. I want to figure: what is the coefficient of friction $\mu$? How high and exceed the maximum return on the plane right body? I know ...
1answer
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### SHM of floating objects

If we consider an object undergoing who has an acceleration proportional to the displacement of the object, it is going simple harmonic motion. In terms of Newton's second law, this is  -\dfrac k ...
2answers
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### Constant of gravity in earth fixed coordinate system

I have this problem: If the constant of gravity is measured to be $g_0$ in an earth fixed coordinate system, what is the difference $g-g_0$ where $g$ is the real constant of gravity as ...
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### How multiple objects in contact are resolved in an inelastic collision, when edge normals don't “line up”

In a case I understand, let's say I have an object A moving at velocity V toward 3 objects in contact B, C, and D: The momentum of A is the mass of A times its velocity. To figure out how the ...
2answers
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### Simple conservation of momentum and frame of reference problem

I'm making a very simple physics engine based on momentum, and I'm solving what response to use for a collision from each involved object's frame of reference. However, something about how I'm ...
2answers
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### Center of mass problem

According to the definition of potential energy, we use $U= mhg .$ In the figure below , A thin uniform rod of mass m and length h is positioned vertically above an anchored frictionless pivot ...
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### Velocity versus time graph [closed]

A stone is thrown at an angle of $45^0$ above the horizontal x-axis in the +x-direction. If air resistance is ignored, which of the velocity versus time graphs shown above best represents $v_x$ ...
2answers
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### Angle between acceleration and velocity

Problem: A particle is constrained to move in a circle with a 10-meter radius. At one instant, the particle's speed is 10 meters per second and is increasing at a rate of 10 meters per second ...
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### Are there problems solvable with Newtonian physics, GR and QM?

First I must let you know that I don't have much understanding of neither GR nor quantum mechanics, and therefore this question. I've mentally pictured Newtonian physics, GR and quantum mechanics all ...
2answers
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### Time period for spring connected body

Two identical springs with spring constant $k$ are connected to identical masses of mass $M$, as shown in the figures above. The ratio of the period for the springs connected in parallel (Figure 1) ...
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### impulse problem [closed]

The figure above shows a plot of the time-dependent force $F_x(t)$ acting on a particle in motion along the x-axis. What is the total impulse delivered to the particle? ...
1answer
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### Why body starts moving when force is applied? [duplicate]

The recent question by m.buettner regarding self-inductance and its resistance to EMF Faraday's law - does the induced current's magnetic field affect the change in flux?, recalled me the ...
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### A space vehicle travelling at a velocity of 1296 (km/h) separates by a controlled explosion into two sections of mass 7276 (kg) and 236 (kg) [closed]

A space vehicle traveling at a velocity of 1296 (km/h) separated by a controlled explosion into two sections of mass 7276 (kg) and 236 (kg). the two parts continue in the same direction with the ...
3answers
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### Relation between the time, velocity and acceleration

This is question from I.E. Iredov's General Physics: $1.22$ : The velocity of a particle moving in the positive direction of the $x-axis$ varies as $v = α \sqrt x$, where $α$ is a positive ...
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