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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Isn't friction on an incline coefficient of friction times the Reactional force?

Question - "As shown in figure a body of mass 1 kg is shifted from A to D on inclined planes by applying a force slowly such that the block is always in contact with the plane surfaces. ...
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Drag force as a function of shear & normal stresses

I would like to understand the relationship between the drag force of an object in a fluid and the microscopic interactions between the object and the fluid particles. Specifically, I would like to ...
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6answers
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Why does the friction act on the inward direction when a car makes a turn on a level road?

I tried looking this question up online but am left a little confused with all the answers, and the diagrams. When a tire of a car negotiates a turn in the road, there exists friction which is ...
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4answers
224 views

The nature of torque as a vector

I can’t comprehend torque’s role properly: 1: What is torque’s nature? Is it some kind of energy? Because its unit is (n.m) and (n.m) is similar to (joules) and it’s energy unit. 2: As we all know “...
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Cause of shear stress while axial loading

The images below are from "Strength of materials" book by Timoshenko. As evident from the text, the author states that stress on the cross section pq can be resolved into normal stress and shear ...
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Symmetries and conservation laws for a falling cat

For Hamiltonian systems, symmetries and conservation laws are defined and related to each other by Noether's theorem. Symmetry means the invariance of the Hamiltonian for a transformation group, and ...
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2answers
168 views

Where exactly is the Coriolis acceleration direction on my picture?

I solved the following problem in my homework: A bullet is fired from a gun towards a target at distance of D=800 meters. The bullet speed is V=800 meters per second. The shot is taken at latitude ...
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2answers
49 views

Why is the force not shown when the body is split into components?

In the given figure, for ease of determining the reactions, the body has been split. The component figures shows internal forces but not the load P. How is this possible ? (Though the figure does not ...
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3answers
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What's wrong with this argument that the potential energy of an arbitrarily heavy object at arbitrary height is $0$?

Consider an object with mass such that there is a gravitational force downward of $1N$. Also assume the environment is a perfect vacuum. Now assume that we exert a force of $1+\epsilon $ Newton upward ...
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5answers
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What causes damage, kinetic energy or momentum?

Let's assume we have 2 bullets. The first bullet has $450$ $J$ of KE and $3$ $kg.m/s$ of momentum, while the second bullet has $250$ $J$ of KE and $5$ $kg.m/s$. Now if they are both shot at ballistic ...
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An Intuitive Understanding of ${{{k^2}} \over {{R^2}}}$

An Example Question- Three bodies, a ring, a solid cylinder and a solid sphere roll down the same inclined plane without slipping. They start from rest. The radii of the bodies are identical. Which of ...
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1answer
118 views

Unclear things about conservation of energy

I have started reading Feynman Lectures in Physics, First Volume, with absolutely no background in physics [*]. In the fourth chapter, conservation of energy, I am having difficulty understanding ...
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Tension in a string attached to different masses

Does tension in a string remain same even if masses attached to it are of different weights? I have provided a diagram, according to me the tension in string should be different as masses hanging ...
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Physics of Athleticism for Dunks

I was curious of the athleticism I'd need to dunk a standard rim at $10$ ft above the ground. Using an online calculator, given that I am $5$ feet $6$ inches tall with a standing reach of $7$ feet $1$ ...
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2answers
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How to determine the minimum force in these questions?

Take a look at this example The author mentioned that the shortest path when the angle is 90 which is clearly obvious. Now take a look at the following problem from the same book The author has ...
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1answer
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Forces acting on an object about to hit the ground

I have a simple question, If I have a spanner or (any object) and I drop it. As it's just about to make contact with the ground what would the main forces acting on it be?
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1answer
43 views

Bathtub boat, is it possible to go forward?

I know nothing would happen when it's just floating. But once I somehow pumped the water to flow out from the shower head, would it keep shooting out water automatically and accelerate the boat ...
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1answer
36 views

When does an oscillating charged particle stop radiating? (classic case)

Although self-force is one of the major problem in physics, I think with a few assumptions it's possible to deal with it, at least in Newtonian mechanics. Let's consider a periodic motion, where we ...
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3answers
139 views

Will a standing wave form when two waves travel at different directions in the same medium?

Is the standing wave just the superposition of two waves travelling in opposite direction in same medium or does it need specific conditions to be formed like frequency and amplitude ?
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1answer
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Forces and their reactions

A body of mass $m$ is placed on a table. The earth is pulling the body with a force $mg$. Taking this force to be the action what is the reaction? Or more generally, Is it true that the reaction ...
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1answer
120 views

Galilean group transformations

My problem is the following: I have difficulties in answering questions (c), (d) and (e). For (c) my answer was $\sqrt{x^{2}+t^{2}}$ and yes, the group forms the group of all isometries since the ...
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4answers
129 views

Regarding gravity force during circular motion

If I spin a ball attached to a string so that the string is pointing diagonally upwards, the centripetal force would be: $$T \cos\theta,$$ where $\theta$ is the angle between the horizontal and ...
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1answer
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Acceleration of free fall at different parts of Earth

“free fall is any motion of a body where gravity is the only acceleration acting upon it.” -Wikipedia Question 1 - If an object is falling freely, will it follow the Earth’s rotation too? Or will ...
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8answers
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Is rotational motion relative to space?

Let's assume that there is nothing in the universe except Earth. If the Earth rotates on its axis as it does, then would we experience the effects of rotational motion like centrifugal force and ...
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4answers
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This is my bucket experiment. I use this experiment to explain lift. Am I right?

Hang the bucket on a long rope. Rotate the bucket to tighten the rope. Then fill the bucket with water and close the lid (shown in the blue line). At this time, the bucket and water are in a static ...
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2answers
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Addition of angular velocities

I'm trying to understand an argument in Taylor's Classical Mechanics section 9.3. Consider two frames, 1 and 2, and a body, 3. Let $\mathbf v_{21}$ be the relative velocity of frame 2 w.r.t. frame 1, ...
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3answers
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Can action force be more than reaction force?

It is weird to ask but i want to know if there is any case where the action force can be more than the reaction force. This question came into my mind when I thought that if a person sits on chair ...
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1answer
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Is tension a resistive force?

The normal force is thought of as being the resistive force that prevents two objects from occupying the same space. In a similar fashion, is it acceptable to think of tension as being the resistive ...
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3answers
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Every action has an equal and opposite reaction. Is is true for torques as well?

So, we studied in classical mechanics that every action has an equal and opposite reaction. So if we apply a force to some object, that object will exert an equal amount of force on us but in the ...
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1answer
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At the Point where Force is being applied, why at that point net force should be zero? [closed]

1st image is of question.2nd is of how i solved the question by considering the F.B.D there. I got the answer which was stated in the book. My doubt is that in the 3rd diagram of 2nd image, i had to ...
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1answer
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Tension about disk

A uniform disk of mass $M = 8.0 \;\mathrm{kg}$ can rotate without friction on a fixed axis. A string is wrapped around its circumference and is attached to a $m = 6.0 \;\mathrm{kg}$ mass. The string ...
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1answer
31 views

Understanding DC motor torque [closed]

I am building an rc car from zero and i got stuck into a little problem.My dc motor torque is 20g/cm and using gears I have achieved a ratio of 125:1 so that means i now have 20*125 = 250g/cm. My ...
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3answers
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Is the acceleration of car greater when hitting the accelerator, or the brakes? [closed]

Is acceleration of car greater than when pedal the pushed to the floor or when break pedal is pushed hard? I do understand that the signs would change in either but I am more considered about the ...
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1answer
101 views

Rigid body dynamics: modelling a polygon bounce off ground

I'm currently making a physics simulator, but I'm having some trouble making a polygon bounce off the floor. I know that collisions are normally modeled as described below by ja72, but I did it ...
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5answers
86 views

Does the law of conservation of momentum mean both linear and angular momentum?

I was solving a problem where a bullet hit a rod hinged about one of its ends. The rod is standing vertically before the collision. We had to find the final angular velocity of the rod. The way we did ...
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1answer
240 views

How to use the concept of variable mass system?

The general equation of variable mass motion is as follows: It's derivation is given below: Refer wikipedia page for more details and the link of it is given below: https://en.wikipedia.org/wiki/...
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3answers
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Conceptual Question: Is acceleration due to gravity positive or negative, and if depending on the situation?

So on brilliant.org, I read a problem where they used the kinematic formula $r_y=v_0T-\frac{1}{2}gT^2$, for when $v_0=120 \frac{m}{s}$ and the magnitude of the acceleration due to gravity is $=10\frac{...
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2answers
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Do you really need force to accelerate or move things when there isnt any gravity and air resistance or any other force acting on the object?

Do you really need force to move things around you if there isn't any force acting on the object? For instance if I try to move a box around and there isn't gravity or any force acting on the box, do ...
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1answer
44 views

For a physical pendulum, why do you use an angular coordinate system when the centre of mass translates too?

I am trying to understand why you can use $F=ma$ for a simple pendulum, yet need the rotational equivalent for a physical pendulum. I understand it is because the rigid body can rotate too, whereas ...
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2answers
35 views

Calculating the power for acceleration of an elevator [duplicate]

An elevator does need some kind of acceleration when it starts to rise up so there has to be s force acting on it. But it surely does not accelerate the whole time so after some distance or time it ...
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3answers
113 views

Potential energy (in lifting an object)

When a man of mass $60 kg$ lifts a mass of $20 kg$ upto height of $20m$. The energy spent by him will be $mgh$. My question is should we add the masses of both the man and the object?. (Competitive ...
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6answers
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What force enables us to walk? Friction or normal reaction?

I know that this question has been asked here before, but I am a little bit confused with all the answers. So when we move, we apply force on the ground in the backward direction. So, is the ground ...
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1answer
69 views

Total energy of a two particle system [closed]

Question: Velocity of center of mass of two particles is $~v~$ and the sum of the masses of two particles is $~m~$. Kinetic energy of the system is: A$)~~=\frac{1}{2}mv^2~$ B$)~~\ge \frac{1}{2}mv^2~$...
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3answers
164 views

Basic question on friction

Consider the whole system initially at rest.Suppose there is friction between the blocks, but not between the lower block and the floor. Suppose I apply a Force F to the left over M, with F greater ...
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3answers
310 views

Angular velocity of two connected pulleys (halved velocity)

I have a problem with this exercise. The weight A is going up with the velocity of 18 cm/s the fixed pulley has the radius of 6cm and the moving one of 3cm. What's the angular velocity of the moving ...
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2answers
122 views

Working with the problems related to potential energy [closed]

Consider a spring mass system. A block is attached to a light vertical spring which is stretched under the load of block and this system is at a height $h$ from the ground. Now my problem is that ...
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0answers
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What are the conditions that an asymmetric top will perform precession in space (zero torque)?

The conditions that an asymmetric top will perform precession under gravitational field are described in the article Precession of an Unsymmetrical Top. (I can't get the full article.) But what if ...
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3answers
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Doubt in a question in Newton's Laws of Motion [closed]

The following question is from JEE (Joint Entrance Examination) 2007. As it is clear from the solution of the problem, they have included only the horizontal component of acceleration and not the ...
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1answer
29 views

Tension in string and Spring force [duplicate]

Why is that a massless string has same tension throughout its length provided the string is inextensible. Similarly in spring block problems we take spring as massless as well and here too we consider ...
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2answers
48 views

What is the exact role of friction in rolling without slipping?

When an object rolls along a plane, we say that for the object to roll without slipping, the velocity of the center of mass must be equal to angular velocity times radius, so that at the point of ...