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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How is the kinetic energy of the wind transferred onto a lift based wind turbine?

The rotor blades of a lift based wind turbine are shaped like airfoils, so the wind flowing around them creates a lift force which in turn moves them around. From a thermodynamic viewpoint and like ...
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129 views

Minimum energy required to roll a cuboid through $90^\circ$ [closed]

I'm stuck on this textbook question about the minimum energy required to roll a cuboid through $90^\circ$ from an upright position to a horizontal position (see image). I believe the correct answer is ...
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3answers
89 views

Confused by answer to mechanics question [closed]

I am confused by the answer to this question. Well, I am trying to explain my thought process about this. I used net energy in the system to calculate the maximum speed. So I assume at max velocity, ...
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50 views

Does Earth also move due to some electrostatic forces?

Does the earth experience some electrostatic forces due to other planets...which also make it move? My question is..whether the earth also moves due to electrostatic force of attraction or only due ...
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2answers
103 views

Why does a reaction force still allow the thing exerting the force to move?

A $5$ kg and a $10$ kg box are touching each other. A $45N$ horizontal force is applied to the $5$kg box in order to accelerate both boxes across the floor. Ignore friction forces and ...
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52 views

Normal force on a banked road & why it's larger than the gravitational force here

Please read this: http://www.askiitians.com/iit-jee-physics/mechanics/banking-of-roads.aspx From my understanding of normal forces, they are a reaction to gravitational or other forces. When a force ...
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62 views

Circular motion from rest [closed]

A particle $P$ is suspended from a fixed point $O$ by a light string of length $a$. When hanging at rest under gravity at $A$ it is given a horizontal velocity $u$. The particle moves freely in a ...
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202 views

A moving brush on a vibrating surface

Hi group, I am a HS student in China preparing for a regional Young Physicist Tournament even. We are very puzzled about why would there be such movement. We would be grateful to see any inspiring ...
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86 views

What causes angular and linear deceleration in a sliding and rotating ring?

I was solving an AP Physics problem involving a ring sliding and rotating over a frictional surface. When I started to think about why the ring eventually comes to a stop I started to become confused. ...
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58 views

Does air density influence a football player's ability to “bend” the ball?

Whilst reading an article on nasa.gov, there was a claim that I found interesting: At higher altitudes, the density r is lower producing a larger radius of curvature and a straighter path. The ...
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94 views

Clarify an assertion on torques from the Feynman lectures

In The Feynman Lectures, vol.I, chapter 18, Feynman discusses torques on a rigid body in two dimensions and says: Now we pause briefly to note that our foregoing introduction of torque, through ...
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46 views

Frequency response of a capstan-like mechanical amplifier

Tension on a wire can be amplified by wrapping the wire around a powered rotating capstan, with output force governed by the linear capstan equation, Tout = Tin * emu*theta. Will this equation hold ...
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115 views

Exam review problem. Weird answer [closed]

The question asks us to calculate the holding force of the triangular mounting if the rock weighs exactly $2kg$ and the mounting supports the rod at exactly $\frac{1}{4}$ of its length. ($g=9.81 ...
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88 views

Difference between kilogram-force and kilogram

I know that a 1 kilogram-force is the force of 1 kilogram acted upon by 1 standard unit of gravity (9.80665 m/s^2). However, in torque descriptions I find that some use $kgf*cm$ while others use ...
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66 views

Coriolis force: why is pole-to-equator air flow eastly?

I have little knowledge in fluid dynamics, so this may be naive. But I have a question while reading a textbook about the Coriolis force, by which the rotation of the earth from west to east changes ...
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65 views

mechanics problem: rope on a fictionless table through a hole

The problem is from "An introduction to Mechanics" by Daniel Kleppner and Robert Kolenkow. The book has a second edition, and the problem is not changed. The number of the problem is 4.16 in second ...
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54 views

Problem about a spring which oscillates due to a external force [closed]

A person holds a spring of stiffness $k= 80$ N/m by its extremity A; In the other end there is a mass of $0.5$ kg. The spring is initially at equilibrium, when the person starts to shake the ...
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27 views

Stair well descent

I am trying to understand the science behind lowering a person down a flight of stairs on a sled. My tensile strength only says it can hold 250 pounds but I have seen it lower people that weigh 300 ...
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73 views

Is this the reason why acceleration is said absolute?

I've seem sometimes people saying that although uniform motion on a straight line cannot be detected and hence it is not absolute, acceleration is indeed absolute in Classical Mechanics (I don't know ...
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67 views

Can Tension between two blocks on a horizontal plane be discovered in these conditions? [closed]

the bodies are linked by an ideal string, one has m1=10kg & the other m2=20kg The force is known and is pulling horizontally, F=60N on the lighter object the coefficient of friction is said to be the ...
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74 views

Angular velocity and instantaneous rotation axis

Let's suppose that we have a cylinder of moment of inertia $I$ rolling on the floor without sliding, moving with linear velocity $v$ and rotating around an axis passing through the center of mass with ...
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55 views

Kinetic and rotational kinetic energy

When a body is rotating on its own axis, and at the same time it is moving, does it possess both KE and RKE? So consider the case of the moon. The moon rotates on its own axis, and at the same time ...
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46 views

Why doesn't $x$ reach a constant for a block experiencing $v^n$ resistive force? [closed]

I am stuck on the Exercise 3.5 of Newtonian Dynamics by R. Fitzpatrick: A block of mass $m$ slides along a horizontal surface which is lubricated with heavy oil such that the block suffers a ...
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1answer
80 views

Do we need Escape Velocity [duplicate]

This may seem silly a lot but I really need some clarification on the necessity of escape velocity for a rocket leaving the Earth's gravity. A stone thrown vertically upwards reaches to a certain ...
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172 views

How do I find the angle given the mass, the acceleration and the force acted on a body?

My Issue I have the mass, the horizontal acceleration and a force that acts on a body. The force forms an angle $\alpha$ of unknown degrees with the x-axis. I would like to know how I can find the ...
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222 views

On the definition of elastic restoring force in a spring

How is the elastic restoring force defined exactly for a spring? We know by hooke's law that $$F_{restoring} = -kx$$ but what does $F_{restoring}$ really mean? I thought up till now that it was the ...
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85 views

Working out velocity (including air resistance) [duplicate]

For my computing project, I am creating a projectile simulator but I cant seem to get my head round the air resistance. I tried by working out the horizontal and vertical velocity by solving it ...
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3answers
715 views

How to find stopping distance of a car? [closed]

I am trying to calculate minimum stopping distance of a car once the brakes are applied. I know the velocity at braking instant, i also know the distance from the obstacle. I found out that $$ d = ...
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2answers
340 views

Can we define tension in a string as the reactive force produced in a string being pulled at both ends?

In my textbook, the definition of tension was given that Tension is the reactive force which exists when string is being stretched at its both end. After it there was a case given that to calculate ...
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126 views

What is causing the normal force in circular motion?

In the picture, at point 2 (the bottom of the ramp) the normal force of the object has a greater magnitude than weight. I understand that the normal force has to be greater than the weight since the ...
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70 views

Determine the value of $g$ with rolling ball

At first, I thought the value of $g$ ($9.8m/s^2$) could be determined simply by placing a ball at the top of a ramp at a known height. The ball was released with no initial velocity, and the final ...
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83 views

When do we assume that a rope has different tensions in different places?

Working a problem with 2 pulleys and masses in class this week the professor at one point assumed that the tension on the two sides of a pulley would be different. Every other time we've done a ...
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4answers
127 views

Conservation of energy, and Newtonian physics that does not fit

Here is a theoretical example where the energy into the system does not mach the energy output. There is no friction or air resistance. A sledge with a rocket engine attached to it is lying still on ...
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52 views

Pendulum forces in orbit

On Earth a pendulum is governed by a set of equations, relating the angle of the swing, the mass etc. However with a pendulum in orbit there is no fixed point (assume 2 masses attached via a string). ...
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60 views

Prove thrust is double the dynamic pressure across a nozzle

I'm trying to teach myself some of the content from 'Rocket Propulsion Elements' by George P. Sutton. After reading over the first couple of chapters feeling like I understood everything, I came ...
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71 views

What happens to KE when lowering a raised book?

I understand the conservation of energy theorem and mechanical energy, but there is this question that confused me a bit, so I hope someone explains it. If you had a book and you raised it, you gave ...
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103 views

Balancing sphere

A cube is balanced on the very top of a sphere, and is given a small push in some direction, at which point it begins sliding down that side of the cube (due to gravity). Now, I want to keep the cube ...
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50 views

Circular motion normal force

Extracted from this article (see the bottom section): Some roller-coasters have loop-the-loop sections, where you travel in a vertical circle, so that you're upside-down at the top. To do this ...
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136 views

Is the work-energy theorem valid for only particles or rigid bodies as well?

Is the work-energy theorem valid for only particles or rigid bodies as well? Most places where I have read this seem to claim the latter. But an example I thought up has been troubling me. Consider ...
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34 views

Acceleration in a system equal for every body — why?

A 1 kg cart can slide frictionlessly on the table. The black weights each weigh 1 kg. The pulleys are frictionless. The task is to determine the acceleration of the cart. For the left-most ...
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1answer
89 views

newton's cradle with 2 balls dropped from same height at same time

I'm creating a logo and want it to be as exact as possible. The logo idea is a "Newtonian cradle", but with only 2 balls and on straight steel wire (can't be bend). What would happen if I dropped ...
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276 views

Spring stiffness calculation problems

I am trying to model a 1 DoF electromagnetic vibration sensor (geophone) analytically and with finite elements. A geophone consists of springs, a permanent magnet and coils. The coils are suspended ...
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211 views

If an object falls - regarding air resistance - does the Potential or Kinetic energy get converted into thermal energy as it is falling?

I read a paragraph on the transfer of potential energy to kinetic energy and heat from this website: Even if air resistance slows down the ball, the potential energy is the same (Mb x g x H). ...
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144 views

Dumbbell rotation

What if apply impulse to dumbbell consisting of two masses and massless rod? It is clear for me that left dumbbell will move straight line. But it is not clear for me what kind of motion will have ...
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114 views

Newton's Principia: Astronomical prerequisites?

I am planning to read the Principia but I currently have no knowledge about Astronomy. What astronomy prerequisites do I need to understand the Principia? I would prefer older books (or "treatises"), ...
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135 views

Work done: kinetic energy or area under F-ds curve?

Starting from $$F=ma = m \frac{dv}{dt} = m \frac{ds}{dt} \frac{dv}{ds} = m v \frac{dv}{ds}, $$ leads to work done = integral of F.ds = integral of mvdv = change in KE. Suppose a variable force is ...
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85 views

Rotational KE in double pendulum

Why the Rotational Kinetic Energy term for the point mass of Kinetic Energy for double pendulum is not included in Lagrangian equation? \begin{align} ...
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76 views

Do components of force have direction when doing work?

When we get angle > 0, the x-component of force is along the direction of displacement and so their product is called Work. So the x-component of force is said to have direction of the respective ...
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70 views

What happens when a force is not applied on the centre of the mass? [duplicate]

The answer to this question force applied not on the center of mass states that for a force applied not directly on the center of mass will have the same linear acceleration as one applied on the ...
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94 views

What is the motion of a balloon with a person climbing on a ladder?

Suppose you had a balloon of mass $M$ in the atmosphere at rest relative to the ground, with a ladder attached reaching towards the ground. A person (of mass less than $M$) begins climbing up the ...