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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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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213 views

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 ...
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334 views

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, ...
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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 ...
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6answers
4k views

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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990 views

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 ...
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109 views

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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2answers
198 views

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 ...
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2answers
420 views

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 ...
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299 views

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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2answers
592 views

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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2answers
118 views

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 ...
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2answers
502 views

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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94 views

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? ...
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1answer
152 views

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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2answers
615 views

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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2answers
162 views

Pressure in fluids

Fluids exert hydrostatic pressure because their molecules hit each other or the immersed body, but why is that at a greater depth pressure is higher when molecules are the same ? Assume density of ...
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1answer
285 views

Modelling the movement and jumps of a chalk while drawing a dashed line on a blackboard

You probably know that if you try to draw a line using a piece of chalk on a blackboard , under some conditions (for example, $\alpha<\frac{\pi}{2}$ in the picture below) you will have a dashed ...
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2answers
154 views

How do objects change their axis of rotation?

If I hold a pencil at its end and spin it, throwing it upwards, it will spin about its end, but will soon start spinning around its center. How is this? I would draw the following torque diagram for ...
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0answers
54 views

Does the slinky base stay perfectly level during the initial free fall [duplicate]

In this related question: Slinky base does not immediately fall due to gravity It is observed that the base does not fall immediately. Obviously the center of mass is in free fall, and the tension ...
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2answers
456 views

How can I solve for time without knowing the vertical velocity?

A guy posted this problem on a forum: There is a bird sitting on a pole of height h. you throw a rock at it and the moment the rock leaves your hand the bird starts flying horizontally away from ...
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1answer
596 views

Pendulum in an elevator

Suppose we have a pendulum tied to the ceiling of an elevator which is at rest. The pendulum is oscillating with a time period $T$, and it has an angular amplitude, say $\beta$. Now at some time ...
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2answers
667 views

Clarification regarding Newton's Third Law of Motion and why movement is possible [duplicate]

Newton's third law states that to every action, there is an equal and opposite reaction. If that's the case, then how do things move at all? Shouldn't all applied forces be canceled by the equal and ...
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2answers
156 views

Will a helicoper which is hovering inside a closed box move with the box when we move it? [duplicate]

I got this micro helicopter to play with, you know that cheap double bladed ones you can find for $25 or so. Anyway last night I was on bed trying to sleep and I got this idea, what if we put the ...
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1answer
135 views

Why is there no such thing as a body in a state of acceleration?

It appears that velocity is a quantity of motion meaning that all objects can have assigned to them a particular velocity. Through the application of forces (ex: gravity, E&m) we measure changes ...
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1answer
50 views

Is this a correct interpretation of pressure?

So I am told that pressure = Force per Area --> F/A.. When considering the units of Force I find that force = kg * m/s^2 When considering the units of Area I find that area = m^2 Thus the units of ...
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711 views

Violation of Newton's Second Law (?) [closed]

Here the big circle denotes the circular path of a stone (small circle on path) tied to a string from the centre of the circular path. This is COMPLETELY HORIZONTAL At an instant the velocity in ...
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142 views

Escape velocity to intersection of two gravitational fields

Find the minimal velocity needed for a meteorite of mass $m$ to get to earth from the moon. Hint: the distance between the center of earth and the center of moon is $\approx 60 R_E$, and the ...
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3answers
396 views

Man in elevator, holding it, on a scale

This is the scenario where my mass is $60 kg$, the mass of the elevator is $30kg$, and due to a malfunction, I have to hold myself and the elevator at rest. The question is, if there is a weighing ...
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1answer
148 views

I read a book saying bernoulli's flight equations didn't have as much impact on lift as most people think [duplicate]

I'm a computer scientist that likes to read about math and physics occasionally. A local author at a nearby aviation center brought bernoulli's flight equations into question. It was clear enough ...
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2answers
3k views

How to determine a reaction force?

An object sits on an inclined plane. The weight of the object will have a normal and parallel component. I always thought that the reaction of the plane was simply the negative of the normal component ...
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1answer
91 views

High School Physics student needs help [closed]

A human cannon has a spring constant of 35 000 N/m. The spring can be extended up to 4.5m. How far horizontally would a 65kg clown be fired if the cannon is pointed upward at 45 degrees to the ...
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0answers
170 views

Determining the length of a Torsional Pendulum

Currently working on this question, however I'm not sure how to solve it. As a pendulum swings in simple harmonic motion at the surface of the Earth, the angle the pendulum makes relative to its ...
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1answer
342 views

Conservation of momentum in collision of two bodies

Suppose we have some ramp on wheels of mass $M$, standing on a frictionless surface. A cart of mass $m$ moves with a certain velocity $v$ towards the ramp. The cart moves up the ramp ...
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306 views

Oberth Effect in deep space

Does the Oberth effect only apply when in orbit of a planet or would a rocket generate more and more thrust (if kept on) even in deep space? Wikipedia explains that the faster the rocket goes, the ...
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1answer
756 views

Gravitational potential energy of mass between two planets

Suppose I want to launch a rocket from earth to some point $O$ between the center of earth and the center of moon (on a straight line connecting their centers), where the gravitational force of the ...
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1answer
157 views

Tension of rope in the gravitational field of earth

Two balls of mass $m$ each one are connected with mass-less rope with the same length as the radius of earth. The system is in free fall. Prove that the tension of the rope when the nearest (to ...
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0answers
47 views

What diameter is used to calculate stress in an elastomer whose cross sectional area changes continuously when streched?

Consider a cylindrical rope of rubbery elastomer with a radius (in inches) equal to the square root of the inverse of $\pi \rightarrow \sqrt \frac{1}{\pi} $ so that the cross sectional area is $1 \, ...
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1answer
349 views

Finding the moment of inertia through superposition?

Let's say I have a body consisting of two homogenous spheres/balls that touch each other. I also have a body fixed coordinate system which consists of that body's principal axes. I know the the moment ...
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1answer
2k views

Projectile along incline [closed]

A particle is projected with velocity $u$ from the bottom of an inclined plane whose inclination with the horizontal is $\beta$. If afterwards the projectile strikes the inclined plane perpendicular ...
19
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1answer
933 views

What determines the angle of the cushion on a pool table?

If you look at the cushions (bumpers) on a pool table, you'll see that they're not vertical. They're tilted inwards. About 10 years ago, I came across a physics exam in which one of the problems ...
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1answer
156 views

Understanding Kepler's $2^{nd}$ law in terms of angular momentum conservation

A) Explain how Kepler's $2^{nd}$ law - "The radius vector from the Sun to a planet sweeps out equal areas in equal time intervals" - can be understood in terms of angular momentum conservation. I ...
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1answer
224 views

Change in speed of a satellite

Suppose there's some satellite orbiting the earth in circular motion. Suppose there's an asteroid that hits the satellite in the same direction as the instant velocity vector of the satellite. The ...
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0answers
49 views

What is to be considered a “body” in physics?

Well, the question says it all; is there a definition of body in physics? What is to be considered a physical object and what it cannot?
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2answers
184 views

How to calculate time for ball to reach plane while considering mass, gravity and wind resistance?

The scenario that I'm having is such that a ball of radius $15mm$ is thrown from a location point $\vec{p}=(2, 5, 2)$ in a direction of $\vec{d}=(3, 0, 4)$. The initial velocity is $30m/s$. There were ...
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1answer
82 views

Rotational Dynamics

In studying rotational dynamics of a rigid body , I can't seem to understand why you can solve the problem correctly only using certain points in a body and not all ? Means angular momentum and torque ...
1
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1answer
776 views

Given a potential energy function, find expression of the force of a particle?

This comes from an AP review packet. I'm given a potential energy functon, $$U(r)=br^{-3/2} + c,$$ where $b$ and $c$ are constants, and need to find the expression for the force on the particle. ...
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1answer
245 views

Firing machine question

Suppose we have a firing machine on a frictionless surface at point $x=0$. It fires a bullet of mass $m$ every $T$ seconds. Each bullet has the same constant velocity $v_0$. There's a body of mass ...
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1answer
77 views

Period of oscilation [duplicate]

Two masses $m_1$ and $m_2$ are connected by a spring of spring constant $k$ and slide freely without friction along horizontal track. What is period of oscillation? No force influence.
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How to determine Center of Gravity? [closed]

I came across this question while having conversation with one person. We know that Center of Gravity of a solid cube is at the intersection of connecting the opposite vertex of the cube. Suppose, you ...