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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Analysis of rolling without slipping

For the following picture that illustrates how we can analyze rolling without slipping by considering the point of contact B to be an instantaneous axis of rotation: It is said that the angular ...
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What if we used extensible string in pulley?

While I was solving questions,I saw that in most the questions, it's written that the used string in pulley is non-extensible, Why? What would happen if we used extensible string having elasticity?
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Shooting two projectiles at the same time with different mass [closed]

Shooting two projectiles having the same radius and in the same condition with the same initial velocity and angle one with a mass of 10kg and the second with a mass of 100kg which one of them will ...
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Two identical items are dropped from the top of a 50-m building. Calculate the landing time delta [closed]

Two identical items, object 1 and object 2, are dropped from the top of a $50 \;\text{m}$ building. Object 1 is dropped with an initial velocity of $0 \;\text{m/s}$, while object 2 is thrown straight ...
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Angular acceleration of a body in free space

A yoyo in vacuum is shown, outer and inner radii are $R$ and $b$ respectively. Point $A$ is in line with force $F$. Method 1 : We can write the torque equation about the centre of mass of the object ...
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Acceleration vector at an extremum

A skier moves along a ski-jump ramp. The ramp is straight from point A to point C and curved from point C onward. The skier speeds up as she moves downhill from point A to point E, where her speed is ...
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Relationship between Angular and Linear momentum

Recently, I came across this interesting problem about billard balls. The question asks us to determine the height $h$ such that the ball rolls without slipping immediately after the collision. The ...
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Unexpected different results from Newton's second law

Please don't ban me. I read through Homework-like questions and I know they should ask about a specific physics concept and show some effort to work through the problem. I hope the question is ok. I ...
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Impulse and Force

When two identical bodies are dropped from different heights, the one falling from a greater height will have more momentum hence a greater impact on the surface it hits. But my question is, force is ...
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How can the jerk tend towards infinity?

Consider a block of mass $m$ kept on a rough surface. A time varying force $F =t$ is applied on the block in a direction parallel to the surface. Assuming the coefficient of static and kinetic ...
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If a bar was from a geostationary satellite to the ground, would it stay stationary?

Suppose there is a perfectly geostationary satellite in orbit, and the satellite deploys a bar or a metal rod from the satellite to the ground, straight down(This is impossible, but hypothetically, it ...
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Travelling along a loop [closed]

A biker is on a mountain of height $h$.From there the biker rolls down and there is a loop through which the biker has to go through.What should be the minimum height of the mountain so that the biker ...
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Is it possible to convert a normal force into a vertical force of a moving object into the direction of travel?

I have read some questions here about normal forces applied to moving objects but I still can't find an answer to the following scenario: So there is an object with a constant velocity and on its way ...
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Newtons Third law - does it apply regardless of size difference between interacting bodies?

This is a theoretical question. Assume I have a $1000 \;\text{kg}$ box and just 1 molecule (say Oxygen) in a 100-meter-tall hollow vertical cylinder. The cylinder walls are much wider than the box ...
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Example on impulse

A rubber ball of mass $50g$ falls from a height of $1m$ and rebounds to a height of $0.5m$. Find the impulse and the average force between the ball and the ground if the time for which they are in ...
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Newtoon´s second law [closed]

In the Atwood machine shown, M = 0.60 kg and m = 0.40 kg. Ignore friction and the mass of the pulley. (a) Calculate the magnitude of the acceleration of the system. (b) Calculate the tension in the ...
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Tension force and Newton's third law

When a horse pulls a cart, suppose connected by a string, it produces a tension $T$ in the string. The cart in turn pulls the horse by an equal force $T$ in the opposite direction. If this T>f, the ...
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Help me in understanding use of vector in this problem

In the question here, velocity of block A is $5 \;\text{m/s}$. To find the velocity $v$ of block B, why do we use $v \cos 53° = 5$ instead of $5 \cos 53° = v$. Isn't the $5 \;\text{m/s}$ velocity ...
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Confusion regarding solution of a problem of conducting spheres

Two conducting spheres of radii $r_1$ and $r_2$ are connected by a metallic spring of stiffness $k$ and natural length $ l \gg r_1, r_2$. A positive charge $+Q$ is slowly delivered to any sphere. Find ...
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Particle over a hemisphere [closed]

A smooth sphere of radius $R$ is made to translate in a straight line with a constant acceleration $a$. A particle at the top of the sphere is released from there at zero velocity with respect to the ...
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1answer
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How can the $x$-components of the frictional force and the normal force be the same for a static block on an incline? [closed]

I recently was assigned this problem as part of my homework: "A block sits on a plane that is inclined at an angle $\theta$. Assume that the friction force is large enough to keep the block at ...
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Is my angular momentum equal to that of the Earth?

Yes, this question sounds silly. However someone who ought to know better insists (with insults) that a person standing on a planet has the same angular momentum as the planet. They certainly have the ...
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Fluid mechanics - Transport Phenomena [closed]

Could someone guide me in this resolution? As the air that will be used to obtain hospital oxygen needs to be free of particles and water, before going to the heat exchanger to condense it must go ...
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How many years does a “bic” pen can work [closed]

How many years does a "bic" pen can work until the cartridge is empty if: we use it 2 hours a day we don't put it at mouth, it is maintained in a normal condition
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Trying to use another method in an-object-collides-with-an-inclined-plane-problem, but why the result does not make any sense [closed]

An object with mass $m$ fell from a certain height and collides with an inclined plane that cannot move with velocity $V$. I want to solve this problem using a little bit different way. This time,I ...
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Can static friction force alone make the center of mass accelerate in this example?

I came up with an idea of motion of ceter of mass the day before yesterday but couldn't find any solid answer for the cause of its motion. Take the example of a man (say of mass $50$$kg$) and a tank (...
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Consider the following figure. A man sits in a pan and tries to raise himself by pullingthe rope downwards [duplicate]

Consider the following figure. A man sits in a pan and tries to raise himself by pulling the rope downwards. Will he be able to raise himself up? Explain. I understand that it is not possible as like ...
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Lagrangian constraint for two pulley system [closed]

The following is a problem from Patrick Hamill's A Student's Guide to Lagrangians and Hamiltonians. A string passes over a massless pulley. Each end is wound around a vertical hoop, as shown in the ...
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How to evaluate acceleration for a body attached with an extensible string? [closed]

I got a problem where they first said the body is attached with an inextensible string. Then it asked to find out the tension and acceleration. At the end they asked what change in your answer will ...
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Potential energy and torque

I know, this may seem as a bit of a weird question. As we know that the relation between force and potential energy i.e: $$F = -\frac{\text{d}U}{\text{d}x}$$ so can we say that relation between torque ...
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What are the physical principles at play when a glass is stuck to a wet table? [closed]

I've decided to write a relatively detailed paper on the following situation, but I'm finding the topic quite hard-to-google. Imagine a glass table with water spilled onto it. Once a drinking glass is ...
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Why an acceleration vector which is perpendicular to the velocity vector does not change the magnitude of the velocity vector? [duplicate]

In uniform circular motion I studied that centripetal force acts on a body which goes in a circle. This centripetal force is required because the body is continuously changing its velocity vector as ...
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Ambiguity in a question from USPhO 2018 [closed]

The 'a.' part of this question mentions that "The block is dropped in such a way that it does not rotate after colliding with the ramp." Lets say we dropped the block such that its bottom ...
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Conservation of angular momentum in a two-body problem

I learned the total angular momentum is conserved in a two-body system. But as far as I saw the descriptions of two-body problem on several textbooks, none of those mention the angular momentum of ...
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Why does a pendulum bob which is hanged to the ceiling of a car go backwards when the car accelerates forward?

Suppose a pendulum bob is hanging to the ceiling of the car. We know that when we accelerate the card forwards then the pendulum bob moves backwards. But why does it move backwards? If it moves ...
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Oblique collision problem

A pendulum is composed of a light rod with length $l$ and an end triangular head with mass $M$ which makes an angle $\alpha$ with the ground. The pendulum is released from an initial angle $\theta_0$ ...
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1answer
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Why work done by tension (like string force) is always zero?

A fixed disc free to rotate about its center (a flywheel) has a string wrapped around it, with a block attached to it. As the block falls, The tension in the string makes the disc rotate. Now, when ...
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What can we say about $\vec{r} \times \dot{\vec{r}}$ in this two-body problem? [closed]

I'm trying to answer some questions about this two-body homework problem. We establish that the attraction force between two particles is given by \begin{equation} \vec{F}_{12} =-k \left( \vec{r} - \...
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Possible value of charges in motion of two charges

Two small particles of charges equal in magnitude and opposite in sign, $q_1$ and $q_2$ have masses $m$ and $2m$ respectively. Initially the distance between the particles is $d$. Both have equal ...
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How could inertial and gravitational mass be even conceptually different?

From https://en.wikipedia.org/wiki/Mass Although inertial mass, passive gravitational mass and active gravitational mass are conceptually distinct, no experiment has ever unambiguously demonstrated ...
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Gyroscope precession: angular momentum and torque

I recently bought a Gyroscope toy online and was keen to find out the Physics behind this fun little "gravity-defying" toy. I did some online research and found a force diagram of a ...
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Example that seems to violate conservation of angular momentum [duplicate]

Mass m is rotating on a horizontal friction-less plane around a tiny hole. A massless string is connected to mass m and the other end of it is slowly pulled. Taking the center as our origin we see ...
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Maximum time of flight in projectile motion [closed]

A body was projected at an angle of $30°$ with initial velocity of $50 \;\text{m}\,\text{s}^{-1}$. Taking $g = 9.8 \;\text{m}\,\text{s}^{-2}$, what is the total time of flight? I have already tried $...
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Finding acceleration in vertical circular motion [closed]

For a $1 \;\text{kg}$ ball being swung in the vertical circular path with a radius of $2 \;\text{m}$, at the instant shown, if the tension force in the cable $OA$ is $5 \;\text{N}$, determine its ...
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Action-reaction force diagrams

I have an issue with the force diagram examples of reaction forces. It doesn't define where the "action"/applied force is coming from. If we were to draw free body diagrams, then for object ...
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A horizontal platform has a mass of 1 kg and on the top of the platform there is a box that has a mass of 2 kg [closed]

a. A force F= 60 N is applied on the platform that causes the platform to accelerate vertically up. What is the magnitude of the force the platform exerts on the box? I have been given the solution ...
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Why doesn't conservation of energy 'work' for collisions? [closed]

A bullet moving with some speed $v$ hits a stationary block and stays in it. How do we calculate the velocity of the bullet-block system post collision? I know how to use conservation of momentum to ...
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About $\frac{d L}{d t}=\tau$ in a rotating center of mass frame

Statement: A Man of mass M stands on a railroad car that is rounding an unbanked turn of radius R at speed v. His center of mass is height L above the car, and his feet are distance d apart. The man ...
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Finding axis of rotation of rigid body

When an object, specifically a rigid body, is hinged, then its axis of rotation is of course about where it is hinged, irrespective of wherever the torque is applied (except an absurd position like ...
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Energy in circular motion

Even if we have to displace an object to a small distance, the object needs to have kinetic energy but when my teacher told me that there's no work done in rotating an object around the center, it ...

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