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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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When a particle moves perpendicularly to it's projection direction

Could anyone please help me with the following: This is concerning the flight of a projectile. Specifically the point in it's flight at which it's velocity vector becomes perpendicular to its initial ...
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Variable mass pendulum (water filled in Bob)?

There is pendulum having Bob made of hollow sphere, having water filled in it. Now at t=0 , a small hole is made on bottom of sphere ,at the same time pendulum is given oscillation. (Assume no damping)...
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Number of collisions with block [on hold]

The problem is given in David Morin's Classical mechanics. Here is the screenshot: Now, I jumped to solve part b of question. To find the number of bounces,we note that mass losses momentum of -2mV ...
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Kinetic energy of disk rotating around axis parallel to the one through its center

Given the situation shown in the figure below. A thin disk with mass m and radius r is rigidly connected to one end of a massless rod with length l at its centre, with the other end of the rod ...
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Why does the GPE of an object always equal the work done?

I had a question that said, "If you do 100 J of work to lift an object over your head, what is the gravitational potential energy relative to its starting position? What would be its gravitational ...
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Which one is easier, pushing downwards or pulling downwards?

Imagine we have a fulcrum, one side is us and one side is a 20kg weight. Which one is easier, to push our side's plate downwards to make the other side move upwards, or to lay under the plate and ...
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Harmonic motion with friction

Consider an undamped mass and spring system with friction. The friction is not proportional to the velocity of the mass. If we solve the corresponding differential equation,the spring will oscillate ...
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Work done in lifting a mass vs work done by mass as it falls to starting position

There are variations of this question on here but I was unable to find exactly what I was looking for so please bear with me if this is old hat. If I start with a mass m at rest at height H1 and ...
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Derivation of friction in interleaved phonebooks

Trying to understand the simple model in https://arxiv.org/abs/1508.03290, describing the friction between the pages of two interleaved phonebooks. Specifically I don't see how to get Eq. 1. Here's ...
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I am confused about which point we should take moment of inertia (moi) in diff situations

A uniform rod of mass m and length l is kept vertical with lower end clamped. It is slightly pushed to fall down under gravity. Find angular speed of rod when passing through its lowest position. I ...
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I have a couple questions about Newton's mechanics [on hold]

i have a couple questions about Newton's mechanics : 1) can you tell me a example where the formula F = dP / dt is necessary? 2) what are the conditions to use conservation of energy? (i think there ...
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mechanics: angular momentum of disk

I am studying mechanical engineering and I've got a problem with the angular momentum of objects that have a rotation which is rather complex to describe like the following: The shaft rotates around ...
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3answers
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Difference between center of mass and center of gravity

Let's consider a very tall building (g would be variable) which is rotating with the earth naturally. Now do the centrifugal force and the gravitational force act on the same spot? If not why does the ...
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1answer
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Newtonian Mechanics cannot be applied in non-inertial frame of reference then how can we apply formula for normal force in an accelerating elevator?

In my physics book there is a diagram in which a block is placed on a table. The table is exerting an upward force $ F_n $ (normal force) on the block and there is a downward force $ F_g $ (...
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Why doesn't the Earth accelerate towards us?

According to Newton's third law of motion that states that every action has an equal and opposite reaction. So, if the Earth exerts a gravitational pull on us (people) then even we should exert a ...
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2answers
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Does potential energy get transferred from my body to a wall when I push a wall and fail to move it?

When I push a rock (and fail to move it), I do not do any work and therefore there should be no energy transfer. But my teacher says that, when one pushes a rock, energy is transferred to the rock ...
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1answer
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How is the normal force on a banked track larger than gravity?

The formula of the vertical force of an object that is not accelerating up or down on a banked curve is: Ncos(θ) = mg There is also a centripetal force component which shows that the normal force is ...
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Changing Coordinate System Changes derivation (mechanics, dynamics)

I'm reviewing some mechanics, and having an issue where my choice of coordinate system results in an incorrect derivation, one that is clearly incorrect. I suspect there's a missing step in my ...
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How does a Foucault pendulum in an Earth-sized centrifuge precess?

Imagine replacing Earth with a centrifugal arm length Earth radius and rotating to produce acceleration g. How does a Foucault pendulum mounted on the end of the centrifuge move and why ? Ignoring ...
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What's the point of momentum?

I know this may sound like a strange question but I have always wondered what exactly the mathematical point of momentum is. I have understood energy to be an attempt to reformulate Newton's 2nd law ...
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1answer
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Will the motion in both systems be same?

In my book, the discussion in SHM is mainly about a mass hanging vertically from a spring. But there are some exercises which contain questions which involves a mass attached to a spring and the whole ...
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1answer
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Total energy, total momentum of two different balls [on hold]

I have a ball out of plasticine thrown horizontally with speed $v$ on a steel ball that is attached from top to the ground on flexible straps in the middle (see picture). The mass of plasticine is $m$,...
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3answers
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Gravitional Potential Energy Formula Magnitude confusion

It is pretty intuitive that increasing the height or distance of an object and also increasing the mass of it increases the gravitational potential energy (GPE). Basically the question is asking, ...
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1answer
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What does the term “no slipping” mean in mechanics?

Say, I have two blocks. One block is on top of the other. Suppose friction is present everywhere. What is the condition for no slipping?
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3answers
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Problem to solve momentum (Classic Newton mechanics) [on hold]

First of all, I want to apologize for my English I'll try to explain my self clearly. I want to share one question about Newtonian mechanics from my homework, of which I can't understand the logic ...
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1answer
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Simple Kinematics question [on hold]

So this is a pretty simple kinematics question I was working on but I completely skipped over a derivation. Here's what I did to solve for the first part: I'm wondering if there is anyway to solve ...
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0answers
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Mass hanging from spring in free fall

Q: A mass $m$ hangs from a massless spring connected to the roof of a box of mass $M$. When the box is held stationary, the mass-spring system oscillates vertically with angular frequency $\omega$. If ...
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1answer
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Why a rope grabbed by a single end seems to follow the hand that grabs it?

Context I am thinking about the physics of the movement of a rope in the context of a person running and grabbing a rope in one hand (the other end is "free", there is nothing attached). When the ...
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1answer
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Explanation of a spring using “Artistotle's law of motion”, $\vec{F}=m\vec{v}$

So I was watching Susskind's Classical Mechanics lectures and I didn't understand something in the second lecture. He was telling about Aristotle's Law of motion which is $$\vec F = m\vec v.$$ He ...
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3answers
356 views

Still Confused about Linear Momentum in a Circle

A point mass with mass $m$, distance $r$ from circle and constant tangential velocity and constant angular velocity is swung around a circle. ($p$ is linear momentum) Angular momentum is radius x ...
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I'm clueless, need help [on hold]

Easy problem but I'm clueless about my approach
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0answers
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Rocket triggering problem [on hold]

If a rocket is to be sent to a body moving with a velocity of 10 m/s from a body at rest at a distance of 1km, if the acceleration of the rocket is neglected and it is moving at a velocity of 50 m/s, ...
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1answer
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D'Alembert's principle and equation of motion

Is obtaining proper equation of motion from D'Alembert's principle a mere coincidence or there is some logic behind this? This is asked because while we are finding the equations in a regime where ...
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Can someone help demonstrate what is easily demonstrable? [on hold]

I am currently starting an intro class to special relativity and quantum mechanics. My first homework involves solving a 1-D collision with a Galilean transformation. I first was going to solve the ...
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Demonstration of simple harmonic motion [on hold]

I have been asked to demostrate that the following object has a simple harmonic motion It is a rigid body and we know its radius ($R$), its mass ($M$) and its moment of inertia $I =MR^2/2$ as it is a ...
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1answer
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How fast can we walk?

It has been a common observation that as and when we accelerate ourselves, there comes a point after which we cannot stay on the ground completely. I wanted to know whether we can find such a maximum ...
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3answers
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Conservation of Momentum within Conservation of Angular Momentum

$L=r \times p$ where $L$ is angular momentum, $r$ is radius and $p$ is tangential linear momentum. Using a generic example of a skater spinning on ice with no friction while being stationary, ...
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I was doing the question in the picture and I don't know why the tension is different [on hold]

I tried solving the question assuming both the tensions same hence my answer was a= (M-m)g/M-m but it is wrong the solution in the book says the tension is different but don't know why is it because ...
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1answer
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Determining $v(t)$, time taken and distance covered by a plane given $a(v)$. Plus, reason why it is unreasonable.

GIVEN PROBLEM: A jet plane landing on an aircraft carrier deploys a parachute to slow itself. The acceleration achieved is $a=-0.005v^2 m/s^2$. a) If the initial speed of the plane is $60 m/s$ ...
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1answer
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Elongation of Spring if Pulled by Unequal Forces

For example, if a spring is pulled on one end by 5N and 3N on the other end and has a spring constant of k=10 N/M, how much longer will the spring become? My first thought was that the Tension in the ...
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2answers
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Are there such things as internal-external forces?

An example of an internal force is the tension in the spring of a harmonic oscillator. An example of an external force is the gravity on a pendulum. Are there any forces that are both internal and ...
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Newtonian mechanics relation with QM [duplicate]

QM is the best theory we have to date for the microscopic world. Can quantum mechanics explain also the motion of an object? In other words can we derive Newtons law of motion from QM?
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2answers
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Angular Momentum of a Rigid body

When defining angular momentum or rather calculating angular momentum what is the difference in the use of the terms "with respect to" , "about a point" or "in the frame of" ? Are the angular ...
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0answers
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Force of gravity [duplicate]

I want to know why isn't the moon fall on earth instead of floating on top or going around the earth without even falling on earth by the force of gravity on earth .
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What determines the direction of an object that has undergone the effect of a gravitational slingshot?

I just started researching this topic and therefore I do not know much about it. Nonetheless, I am still curious about what determines the direction an object takes after passing by a planet. I think ...
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0answers
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Simple Lagrangian Example [on hold]

Consider a mass $m$ placed at the topmost point of a wedge of mass $M$. The wedge is free to move on the smooth floor. What is the acceleration of the wedge and the block when the system is released ...
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1answer
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Torques in Euler equation

The Euler equation is given by $$\mathbf I\dot{\boldsymbol \omega}+\boldsymbol\omega\times \mathbf I\boldsymbol\omega= \mathbf M.$$ Also see here. It explains that The expressions for the torque in ...
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5answers
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Why does a point mass make a certain angle with a force exerted on it?

In real world, I see that if I hit (physicall speaking exert a force on)a marble or billiard ball properly (I think in its center of mass) it goes in a straight line with the force which means the ...
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2answers
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Whats the cross sectional area related to shear stress in torsion of a bar?

In shear force in a rectangular bar,the relevant area is the cross sectional area parallel to the applied force.But in torsion which also undergo shearing we get shear stress from torsion equation.I ...