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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What is the need of acceleration?

As we can usually predict the various forces that a body might be undergoing based on its position and its velocity.Hence what is the need of acceleration?
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Understanding the geodesic equation in a Wikipedia article

I was reading this Wikipedia article which attempts to motivates some concepts key to General Relativity in the Newtonian setting first. However I was not able to understand one of the equations ...
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Determining circular velocity of an object in a sphere from gravity

The radius of a sphere is $12$ m. An object is circulating around the sphere such that it is touching the edge of the sphere and close to the bottom such that its radius is 9m. As it slows down, the ...
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Discussion regarding work done?

Let's consider a very basic physics problem involving pushing a block with a frictional force. These kinds of problems are common in introductory physics textbooks—but they often miss some subtle ...
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Why are you accelerating yet remaining at a constant speed while going around a curve? [duplicate]

We have to write a rap in physics, and it has to answer a prompt he gave us on this packet. The prompt for the verse I am writing is: Pretend you are driving a car on the freeway going 65 mph. The ...
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Direction of friction in pure rolling

Suppose a disc or a sphere with uniform mass density is purely rolling without any slipping/sliding on a ground having friction. Will there be friction acting on the disc/sphere? If yes, what will be ...
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55 views

What is the true quantitative definition of “force”? [duplicate]

Newton's second Law of Motion states that for a point mass, $\vec F = m \vec a$. This is a law and not a definition. So, this law only makes sense if all the physical quantities appearing in this law ...
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247 views

Displacement of string and simple harmonic motion

If the displacement of a string follows $$ y(x,t) = A \sin(kx - \omega t + \phi_0) $$ how can I show that the "hand" generating the wave must be moving vertically in a simple harmonic motion? ...
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Angular velocity in Body-fixed frame and space-fixed frame

When we solve for a free symmetric top we find that in body fixed frame, the angular velocity precesses. My confusion is regarding the calculation of omega in body frame. When i am in the body fixed ...
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How do you calculate how heavy you feel from negative g forces?

My physics tacher told me that to calculate the weight that you feel from negative g forces you have to devide your mass by the negative g force, but then my friend told me that it did't make sense ...
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37 views

Work done by force with changing angle [on hold]

There is a 20kg block attached to a spring which is released from rest. The initial elongation of spring is 1 m. Its being pulled by constant horizontal force of 50N. We have to find its velocity in ...
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Why is resultant displacement in an composition of simple harmonic motion the sum of individual displacements?

I recently came across the concept of the composition in simple harmonic motion. A paragraph says that: If $$x_1 = A_1sin(\omega t)$$ $$x_2 = A_1sin(\omega t + \phi)$$ Then, the resultant ...
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“Newtonian limit” property of special relativity

Books say that special relativity is indistinguishable from Newtonian mechanics when the speed of the primed frame ($v$) is small compared to the speed of light ($c$). This is what I mean by the "...
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Can you get a playground to swing from stationary

I feel this might be a FAQ but I would love a definitive answer. Imagine a frictionless stationary idealised child's playground swing. If you are sitting on the seat of the swing, is it possible in ...
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How much weight do you feel during negative g-forces?

My physics teacher told me and some other students that when you experience negative g-forces, your weight equals: $$\frac{mass}{g_{force}}$$ So when the g-forces equal -4 g your mass will be: $$\...
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5 Lagrangian points: why isn't there a line of stability between $L_1$ and $L_4$ and $L_1$ and $L_5$ respectively? [duplicate]

Given the 5 Lagrangian points of two large orbiting bodies: (from wikipedia), why isn't there a line of stability between L1 and L4 and L1 and L5 respectively (as depicted in red in the modified ...
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What is the definition of the “characteristic radius”?

Upon solving exercises regarding relativity, I have run into the problem below. The inverse square radius of curvature of spacetime is of orer the tidal field, $R^{-2} \approx \nabla^2 \phi$ where $\...
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Torque exercise problem

I am learning physics with help of this site https://www.khanacademy.org/ And I have stumbled upon a task that I can not completely understand The task says: A gasoline engine producing Nm of ...
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Is “Total Energy = Kinetic + Potential” always true in a harmonic oscillator?

Consider a object executing simple harmonic motion in one dimensions due to a variable external force (like a spring maybe). I like to think that at any point in it's motion at any time the mechanical ...
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Feynman screwjack problem

What is a thread? How does he know you need to turn the handle "around" 10 times? From where does the 126 inches come from? I thought Feynman explanations were easy... Let us now illustrate the ...
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So, DO All Things Float In Space, Or Not?

Incredibly, I cannot find an answer to this anywhere. The experts say that planets etc don't actually float in space, but instead continuously 'freefall' around the object they're orbiting and so on. ...
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When two people are pulling a rope, how come the force at the center of mass of the system(the tension on some specific point at the rope) is not 0?

Imagine two people of equal mass are pulling a rope in different directions. At the midpoint on the rope, why is the force acting not equal to 0? Its the same issue if I hold two newtonmeters, attach ...
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Block on trolley [on hold]

A block is placed on the trolley. It is found after calculations that the block is at rest with respect to trolley when the trolley is accelerating. When acceleration of trolley is zero what will be ...
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Why is this system isolated (revised)?

(Image updated for clearance) Hello, Assuming that there is no friction anywhere and both box 1 and ramp 2 start at rest, I was wondering why this is an isolated system in terms of momentum ...
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Feynman screw jack device

Feynman mentions in his book, The Feynman Lectures on physics Let us now illustrate the energy principle with a more complicated problem, the screw jack shown in Fig. 4-5. A handle 20 inches long ...
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3answers
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How to conceptualize Newton's apple?

I have no physics background, which is the genesis of my question. In pop-science, it is frequently mentioned that Newton's apple didn't fall toward his head, but rather that his head came up and ...
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Can you ever exert more downwards force than your weight?

So, because I'm a hardcore person, I risked all this afternoon by going out in the wind, the rain and the cold to construct a willow den. Yes, it seems a menial task, but it was actually quite ...
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3answers
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Newton's Third Law in an elevator

Some misconception I'd like cleared up. From what I understand, when an elevator accelerates downwards with you, there must be a net force acting downwards on you. Since your true weight remains the ...
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1answer
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Idea to measure speed of a cricket ball by its pressure impact

I am going to start a project where I need to check that if the cricket ball is hitting on a particular area on ground second the speed of this cricket ball. I need one solution which can fulfill my ...
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Why doesn't Newton's third law mean a person bounces back to where they started when they hit the ground? [closed]

Why doesn't a person bounce back after falling down like a ball does? If we push a person and he falls down then why doesn't he come back to his initial position? According to Newton's 3rd law of ...
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How the ladder will slip if the wall and ground were to be smooth?

If I have a situation like this Where my blue thing is wall and the yellow thing is the ground. If both were to be smooth then they will exert a contact force only normal to them which I have ...
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If an object moving in a circle experiences centripetal force, then doesn't it also experience centrifugal force, because of Newton's third law?

When an object moves in a circle, there's an acceleration towards the center of the circle, the centripetal acceleration, which also gives us the centrifugal force (since $F = ma$ is the equation for ...
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Change in position of center of mass [on hold]

A man is climbing a balloon. Will the center of mass change its position as the man climbs up in vertical direction? As there is an external force (weight of ballon and weight of man), then why will ...
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Why do I get a non-zero Coriolis acceleration for a reference frame that moves in a straight line without rotating?

When you have a stationary reference frame $\{O', (\pmb{e}'_1, \pmb{e}'_2, \pmb{e}'_3)\}$ and a moving reference frame $\{O, (\pmb{e}_1, \pmb{e}_2, \pmb{e}_3)\}$, my textbook defines the Coriolis ...
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2answers
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Rotation and potential energy [on hold]

Please read the question. The solution to this is that since it is a hollow cylinder Ratio of Rotational Kinetic Energy and Translational Kinetic is 1, hence KE (T) = mgh/2 and finally on right ...
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4answers
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Doubt relating pure rolling

As we know, when an object perform pure rolling on a plane having friction the friction acts on the edge in the direction opposite to the direction of its translational motion. There are no other ...
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Sliding down a spherical ramp [on hold]

A ball of mass M starts at the top of a quarter circle ramp of radius R. The ramp is completely friction-less. What is the height of the ball and x position of the ball as a function of time? My ...
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1answer
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The vibration of mechanical ondes

i want to ask about the relation highlighted in yellow in the picture the equation of motion of this system can be obtained using the Lagrange formalism, but my question is about this relation i have ...
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1answer
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Newton's cradle faster than light?

If we have a Newton's cradle toy where the balls actually touch each other. Can energy be transferred from the first ball to the last one faster than the speed of light? And what factors control the ...
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How do I convert the torque of a motor into usable data for predicting projectile velocity? [on hold]

So I am trying to build a 2-motor setup to launch a soccer ball about 20-30ish yards. I started looking up motors and found that the way all of them describe how powerful they are is in horsepower. ...
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1answer
48 views

Computing total derivative of Kinetic Energy w.r.t time

I am confused as to how to take the total derivative $\frac{dKE}{dt}$, where $KE$ is the kinetic energy. I know that $KE = 1/2 *m * \dot{\vec r} \cdot \dot{\vec r}$. From here, if I take derivative ...
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What physical interpretation can we derive from this experimental step up?

(This is not a homework question!) An experimental set up shows 2 rigidly placed stands, with pieces of metal links joining with each other forming a chain. The chain is hung from the top point to ...
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2answers
238 views

Why do we only feel the centrifugal force?

After spending some time researching about the centrifugal force, I now understand that it is needed in a non-inertial reference frame for Newton's Laws to hold true. However, I don't understand why ...
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2answers
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Friction force in rolling motion

In rolling without slipping motion we know that the friction acting is static friction and so we treat it as an unknown while solving equations of dynamics. Question: Is the static friction during ...
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2answers
616 views

Influence of couple-moment's position on bending moment diagram

The moment of two equally opposing force would create a couple-moment. Since the couple-moment value is invariant to the point considered to calculate the couple-moment, I can replace the two equally ...
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About tension in spring [on hold]

I have confusion related to tension in string. I know that spring force does not changes immediately.But what happened to tension T in string when we cut spring k1.Does it change or remain same.And ...
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3answers
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Derivation of Conservation of Energy from Newton's Second Law [duplicate]

Given Newtons's Second Law: $$ \frac {d}{dt} (m \boldsymbol{\dot r}) = \mathbf F $$ How is it possible to derive the conservation of energy equation with a constant mass? That is how can you derive $ ...
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3answers
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Will a can filled with vacuum move when we let in air? [duplicate]

This picture is from L.C.Epstein's book Thinking Physics. The upper can is filled with compressed air, and, when an opening is made on the right, the air comes out and the can shoots left. The ...
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2answers
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What happens, if a rocket is filled with a vacuum instead of high pressured air?

Suppose you put wheels under a compressed air tank so that it can move horizontally to the right and to the left. Suppose there is a nozzle on the right hand side of the tank (in the picture on the ...
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2answers
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How to spin a fidget spinner with maximum velocity?

Physics doesn't always come in the form of books. It also comes in the form of toys. So, I came across this fascinating toy that spins two minutes straight when given a spin. I got a chance to use ...