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 concepts, use [classical-mechanics]. For Newton’s description of gravity, use [newtonian-gravity].

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How come $X^2$ is a physical function?

This might be a very dumb question. When we use values that are lower then one in lets say, the expression for kinetic energy - $\frac{1}{2}MV^2$, (for example $V=0.9\frac{m}{s}$ or $V=0.8\frac{m}{s}$...
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Work and energy: conceptual doubt

Suppose I am sliding a block very slowly on a rough surface. If the block has travelled $d$ distance then work done by me is $W_1=\mu mg d$ and that by friction is $W_2=-\mu mg d$. Now the energy ...
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Car moving on the hill (circular motion) [closed]

I have the following question which makes no sense to me: Car is moving at $20 \;\text{m/s}$ speed on the road. Curvature radius of the hill is $R = 100 \;\text{m}$. What is the maximum possible ...
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Trying to find constant of motion formula [closed]

I have a ball that oscillates around a point. The ball have an origin and a destination (the point where the screen is touched). This destination is the equilibrium. One operator gave me this equation ...
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5answers
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Is “non-inertial” frame a relative term?

I've heard only two definitions of non-inertial frame so far: I. A frame that is accelerating with respect to an inertial frame. II. A frame where Newton's Laws are invalid. Let's begin with ...
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Could you determine if you were moving when standing on an infinite, frictionless plane?

I'm quite curious to know about this question. I don't really fully understand how inertia works so I couldn't quite put this one together in my head. As far as I know, if you are moving in empty ...
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1answer
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How to find the momentum of an object at time $T$ when velocity is not given? [closed]

I tried finding the change in momentum which is force x change in time. Here, I assumed the final momentum would be equal to change in momentum as since at $t= 0$, the object is at rest. However, I ...
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1answer
48 views

Angular vs tangential vs centripetal acceleration of a non-rotating object [closed]

I was presented with a physics problem which asks to determine the maximum angular acceleraion. Unsure of how to do this, I did some research and came across the terms angular, tangential and ...
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1answer
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Stuck with this problem. Is the resultant velocity when the swimmer is going along the river just the resultant velocity of swimmer and river itself? [closed]

Here, I tried to find the resultant velocity when the swimmer is swimming perpendicularly with respect to the speed of the river. However, I got option C, which was not the right answer. Is there ...
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Hooke's Law and work done [closed]

The formula for potential energy of a spring is $(1/2)kx^2$, with $k$ = spring constant and $x$ = displacement. This is the integral of Hooke's Law, $F = kx$. My understanding is that given a ...
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Solution to pendulum differential equation

In a chapter on oscillations in a physics book, the differential equation $$\ddot{\theta}=-\frac{g}{L}\sin(\theta)$$ is found and solved using the small-angle-approximation $$\sin(\theta)\approx\theta$...
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What force is acting on the container?

Foreword: I have been trying to solve this problem for several days: [Does diffusion cause the bottle to move to the left?] But the answers presented there are contradictory. Some say the bottle will ...
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How do we get $p_{\psi}=M_3$ and $p_{\phi}=M_z$ for a symmetrical top?

I am working on Landau and Lifshitz's Mechanics, 3rd edition. In Section 35 Problem 1 it studies a heavy symmetrical top. We know that the Lagrangian is given by $$ L=\frac{1}{2}(I_1+\mu l^2)(\dot{\...
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Common assumptions in simple physics questions [closed]

I have the following problem which specifically asks me to assume and justify additional information. I was wondering if there were common assumptions across simple physics problems like this that I ...
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Classical mechanics spring block system [closed]

Two blocks of mass $m_1$ and $m_2$ are attached at the ends of an ideal spring of force constant $k$ and natural length $l_0$. The system rests on a smooth horizontal plane. Blocks having mass $m_1$ ...
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Deriving Newtonian Gravity from General Relativity? [duplicate]

Let me provide some insight, I was studiying about General Relativity, and I read that it "encapsulates" Newtonian Gravity. I understand this perfectly, because, Einstein used lots of ideas ...
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Why the path of a balloon left untied is unpredictable but of a rocket is predictable? [duplicate]

When a water rocket is projected, it goes in a specific trajectory. But when a balloon is inflated and left untied, it does not follow a definite path. It goes in a random way. I do not see any ...
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Discuss the possibility of using force rather than mass as the basic quantity. (Kibble, Classical Mechanics)

I'm starting first year in the Autumn and I'm doing some pre-university maths and physics. One of the questions I had a go at doing was this one, from Classical Mechanics by Kibble: Discuss the ...
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SHM of a block attached to two springs and two light pulleys [closed]

The question I have is shown in the figure below: (Please note that all pulleys are ideal and massless). I have tried this question for a bit, and I'm attaching my work below. But the answer for the ...
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1answer
28 views

Measuring work by lifting cable with constant weight

At calculus - an intuitive and physical approach by Morris Kline(2nd edition) 143p, A cable weighing 2 pounds per foot of length (and so having a mass of 2 pounds per foot) is suspended from the top ...
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3answers
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Non-inertial reference frame, a pendulum in an accelerating car [duplicate]

Take a pendulum that is suspended in a car; it hangs from a rope in a car. When the car starts to accelerate with acceleration $a_0$ to the right, from an inertial frame, Why does the pendulum move ...
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4answers
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Really understanding Newtonian mechanics [closed]

I absolutely abhor the way in which physics is taught at school. All they really do is prepare you for doing physics problems, making little effort to impart an actual understanding of the subject ...
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Physics of Formula 1 [closed]

I'm a second year student in Engineering and a big fan of F1. I was wondering if there were any books to understand, from a physical and scientific point of view, how an F1 car works. I'm not looking ...
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Reaction force cancels out? [duplicate]

Lets say Im pushing on the wall with a force of 1N. According to newtons laws the wall will push me back with a force of 1N. What I dont get is that my hand already has this 1N of force meaning when ...
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Simple (classical, non-damped) 1D harmonic oscillator - how to represent phase space elliptical trajectory in polar form for an ellipse?

Considering a classical, non-damped 1D harmonic oscillator (e.g. mass $m$ oscillating along $x$-axis attached to spring with constant $k$) -- described by Hamiltonian (for constant energy $E$) $$E=p^2/...
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Who moves when an object falls by gravity?

I'm reading calculus book by Morris Kline. This book treats physics because calculus grew out of physical and geometrical problems. I have no background about physics and got a question while reading ...
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Why does twisting a cork make it easier to remove from a bottle?

When we want to remove a cork from a bottle first we turn the cork. Turning in one direction makes it easier to remove in the axial direction. Does anyone know something more about this?
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Why does the ball not climb the same height when released from a particular height in a double inclined plane even when the surface is frictionless? [closed]

According to the textbook, the ball will nearly climb the same height (a little less but never greater), why? I came across a question in SS Krotov where it was asked why does the ball not climb the ...
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1answer
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The effect of velocity on the $g$-force applied to the pilot

In a level flight (not maneuvering), if an aircraft increases its velocity from Mach 0 to Mach 10, how much $g$-force is applied to the pilot? Is that any equation for it?
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Effective gravity in simple pendulum [closed]

Let a simple pendulum be on a car moving on a horizontal road. I was supposed to find its period, in my book it simply says that effective gravity is $\sqrt{a^2+g^2}$ and wrote the time period as $2\...
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Why linear displacement is length of the arc?

I mean isn't the word itself says "linear" meaning straight and "displacement" meaning shortest path between two points? we even used equations of motion in circular motion like $...
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Question about the direction of Centrifugal and coriolis force

I can't understand how the cross product of $\hat{\mathbf{z}}$ and $\hat{\mathbf{r}}$ works in the equation of centrifugal force and the same cross product between $\hat{\mathbf{z}}$ and $\hat{\...
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Find a general solution for gravitational potential, $\Phi(r)$ in a uniform, Newtonian universe, to derive Friedmann equations with $v_r = rH(t)$

I want to derive the Friedmann equation in a Newtonian regime, but properly. So, I am supposed to consider a cold fluid with density $\rho$, velocity field $v$ and gravitational potential $\Phi$. By ...
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Newtons third law of motion [duplicate]

Im having a real hard time understanding how newtons third law works. Say im accelerating a 1kg ball to 50m/s^2. This means that im applying a force of 50N on the ball. Newtons third law tells us that ...
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4answers
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Alternative universes without max speed and with absolute time

I'm not asking of something real but something mathematically possible. Is it possible to do a math model of an universe (not ours) without max speed and without time dilatations? What would be the ...
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2answers
63 views

On the idea of an inertial frame of reference and its theoretical interest

An inertial frame is often defined as (1) a frame that is not accelerated (2) a member of an (equivalence) class of frames , that is , the class of frames that are in constant rectilinear motion with ...
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How to know unstable and stable orbit from a given potential? [closed]

A particle of mass $m$ having a non-zero angular momentum of magnitude $l$ is subjected to a central force potential $$V(\vec r)= k\ ln(r) $$ where $k$ is a constant and $r =|\vec r|$, what is the ...
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Why is the resultant of the two forced equal to the force $F$? [closed]

Three chains act on the bracket such that they create a resultant force having a magnitude of 500 lb. If two of the chains are subjected to known forces, as shown, determine the angle $u$ of the third ...
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Analysing the collision of an elastic body with a rough surface

An elastic cube sliding without friction along a horizontal floor hits a vertical wall with one of its faces parallel to the wall. The coefficient of friction between the wall and the cube is $\mu$. ...
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Motorcycle multi-body model and internal torques

In deriving a model for the in-plane dynamics of a motorcycle and I am facing the problem of reactive torques. The model is a multi-body system, where the bodies of interest are rear wheel, swingarm ...
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Need help with question (schoolwork) [closed]

Need help with question $7b$. the answer is $27 ^\circ$ but unsure as to how you arrive at that conclusion.
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Why is the reaction force same in magnitude to the action force in Newton's third law of motion?

In Newton's $3$rd law of motion, it states that All forces between two objects exist in equal magnitude and opposite direction How did Newton knew exactly that the "reaction" force will be ...
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How to obtain maximum height of a ball thrown in a circular frame? [closed]

I am trying to calculate the maximum height a ball can reach in a rotating reference frame. As seen below, the ball can follow a path such as this. I am aware that this path is symetricall, so if I ...
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4answers
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Will this move due to pressure difference?

A U-tube is placed on a frictionless horizontal plane with a cork fixed tightly at the middle of the horizontal arm. It is filled with water and mercury on either side, as shown in the picture. Let's ...
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How to find time at any point on the path of a projectile motion?

I know how to find the time of flight and all but what if I chose a random point on the path of the projectile (no air resistance) and ask the time at which the particle is present there, then how can ...
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Conservation of angular momentum - why can't $\textbf{r} \times$ be replaced with arbitrary continuous function?

None of Newton's laws of motion, directly states the conservation of angular momentum. For a point mass it's obvious and can be derived from momentum conservation just by taking the cross product with ...
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3answers
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How does friction accelerate a car after rest?

If a car moves using the friction force from the rotation of the wheels, shouldn't a car be unable to accelerate immediately after the car is at motion, since there will be a friction force of equal ...
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2answers
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Why does Drag force equation contradicts the relationship between Reynolds number and drag coefficient?

The drag force equation is described as: $$ F_D = \frac{1}{2}\rho v^2 C_D A $$ Where the cross-sectional area of the front of the sphere is = πr^2, so we can deduce that the radius and drag ...
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5answers
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Friction is also a conservative force?

I have asked a recent question about how spring force is conservative and in that I learnt that for a force to be conservative the work done by the force should be path independent given the initial ...
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1answer
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A question about classification of constraints

I am a mathematics student. I have lagrangian and hamiltonian mechanics as an elective I have taken in this sem. Today I had a test in which I was asked a question: A ball is constrained to move ...

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