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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The physics equation for a perpetual seesaw

I am trying to create a game that envovles two or more people jumping on a seesaw and propelling each other in the air. I need help with the physics equations Assume no friction no air resistance ...
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1answer
290 views

Why closed bottle change its weight when I put effervescence tablet?

I use several shape, several type of material (glass, metal, plastic), I use two different balances with 0.01g of accuracy. I put oil on gasket, and put upside down (like that I can see if water ...
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286 views

A man pulling himself up on a platform

Consider the following image: Is it possible that the man pulls himself up (suppose the weight of the platform is negligible), or just lift the right part of the platform up? How to analyse this ...
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172 views

Ball on a slope [closed]

I have a lab report, but I can not write it in a correct way. The lab experiment was about a ball rolling on a slope, I have a height of the slope, the distance, and the time in which the ball spent ...
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2answers
233 views

Mathematical model for this graph of a simplified binary star system?

Unnecessary background for question: I had a school assignment asking us to relate a quadratic equation to a real life example relating to our future dream career, making sure to express the accuracy ...
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4answers
2k views

Time period of simple pendulum with varying mass

How do you find time period as a function of time for a simple pendulum that is in the form of a hollow sphere that is filled with mercury and there is a hole in the bottom through which the mercury ...
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1answer
588 views

Solve a problem of work and energy

A man pulling sled of his daughter by a massless rope, climbing a snowy hill whose slope is equal to 15 °. Considering that the mass of the sled is $4Kg$, the girl's $26Kg$ and $\mu _c = 0,25$, ...
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1answer
389 views

Two-block system connected to a spring

Say you have two blocks with masses $m_1$ and $m_2$, where $m_1>m_2$. The smaller block sits atop the larger block. The larger block is connected to a spring, which is then connected to a wall a ...
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479 views

Deriving the rocket equation

Recently I decided to brush on the those parts of classical mechanics that always gave me trouble. One of those parts was the rocket equation so I figured that I would try to derive the appropriate ...
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126 views

Question about moments? [closed]

Take a look at this diagram: http://www.chegg.com/homework-help/questions-and-answers/7-pipe-assembly-supports-vertical-loads-shown-determine-components-reaction-ball-socket-jo-q2260091 If you ...
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3answers
871 views

Resistive force proportional to velocity

Find the displacement and velocity of horizontal motion in a medium in which the retarding force is proportional to the velocity. I kind of understand how to do this problem. We know that the ...
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2answers
460 views

Does the velocity of a falling object increase as the mass of a object increases?

I am doing an experiment to show the effect on the velocity of a falling mass due to change in mass. How can i justify my prediction that the velocity of the falling mass will increase as i increase ...
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4answers
930 views

Gravitational Potential Energy (GPE) to Kinetic Energy (KE) transfer in Satellite Orbits

I am stumped by a mundane A Level Physics question (teacher of physics here obviously a bit short of practice!). My colleagues and I are stumped and were wondering if any one could help us. It ...
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1answer
91 views

Racing balls question

My question is related to simulation of racing ball demonstration. http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=142 One ball goes on a straight path, while another one goes on a curved path. ...
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2answers
503 views

Finding the velocity of a block down an incline plane after in moves a distance $x_0$

Consider a block sliding down an incline plane at an angle $\theta$ with the horizontal. For the acceleration as a function of $\theta$ I find $$\ddot{x}=g \ \sin\theta $$ My text then claims we can ...
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0answers
356 views

Moment of inertia about a tilted axis

I apologize if it seems foolish, I am a beginner. Suppose I am given an object, whose moment of inertia along the x,z axes are known. Suppose it rotates around a tilted axis, ...
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1answer
893 views

Two hanging masses connected by springs

I had this problem for a candidacy exam, but wasn't able to get the complete answer. Their spring constants and masses are not the same, find the equilibrium position and frequencies of the system. ...
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2answers
125 views

Circumference of a circular path

Suppose a car moves with a constant speed of $20 \text{m/s}$ a quarter of a circle, and completes the quarter in $5$ seconds. One way to calculate the circumference is simply $20 \cdot 5 \cdot 4 = 400 ...
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2answers
1k views

Conservation of momentum when friction is present

Conservation of momentum applies when net force is zero. Suppose that there is a system of a canon and a canonball. Total momentum of the system is zero before canonball is fired. Now canonball is ...
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55 views

space acrobatics

In the newly released movie "Gravity" the main character is left alone floating in space in spacesuit, in a fast spin. Assuming there are no external forces (no tether, jet-pack etc) the system is ...
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1answer
284 views

Why can you add moment vectors?

My book says the following: If the body is acted upon by a system of forces, the resultant moment of the forces about point O can be determined by vector addition of the moment of each force. The ...
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2answers
138 views

Forces, Incline, and Mass

A farm tractor tows a $3900 kg$ trailer up a $16^\circ$ incline with a steady speed of $3.0 m/s$. What force does the tractor exert on the trailer? (Ignore friction.) I am having trouble ...
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3answers
336 views

Nature of frictional force

I was thinking about a situation where a person in standing on the ground with some friction. The frictional force is directly proportional to the normal reaction acting on him by the ground. Assume ...
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2answers
800 views

Dynamics of counter-rotating flywheels

I've wondered about this for ages. If we create a pair of flywheels that rotate in the opposite direction with the same angular momentum, but are co-located and have the same mass and inertial moment ...
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2answers
292 views

Would this box on the floor rotate based on friction?

There is a floor that friction is proportional to its velocity (like $F=-kv$) and there is a box with its width as $l$ and its height as $h$. (you may assume that $l$ is longer than $h$). It is on the ...
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248 views

Conservation of angular momentum

We were learning about angular momentum in class today, and although it sort of makes sense, it's much harder for me to think about than linear momentum. So from what I can tell: Angular momentum ...
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1answer
157 views

Finding the tangential force experienced by a bob of mass m on a simple pendulum via the gradient/nabla operator)

The problem was posed as follows. Given a pendulum of length $L$ with a mass $m$ attached to it, which forms an angle $\theta$ from the y-axis to the direction of swinging. First we had to find the ...
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164 views

Classically, how can an electron orbiting a proton radiate given its relativistic energy

In classical relativistic Electrodynamics, we are often told that any accelerating point charge inherently radiates (Bremstrallung). (This is the basis for the need for a QM conception of electrons.) ...
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705 views

Why does the amount of energy transferred depend on distance rather than time?

The change in energy of an object can be determined by the work equation, where work is the change in energy: $$ W = F \cdot d $$ I conceptualize the transfer of energy as simply a series of small ...
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309 views

Does a different opposing force affect work?

Suppose a man exerts $10~N$ as he lifts a $1~kg$ box a distance of $2~m$ against Earth's gravity. To determine work we can use the following equation: $$ W = F \cdot d \\ W = (10~N) \cdot (2~m) = ...
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367 views

$\gamma$ in Newton's Second Law of Motion in Differential Form

I am teaching myself Differential Equations from a website. In the website I am up to Direction Fields and an example of a differential equation is Newton's Second Law of Motion. It is written on the ...
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1answer
256 views

Action and reaction in case of a falling object

Let us say a hard object is falling on a stack of pillows. At the point of contact, it will experience a force equal to its weight and would be at rest if it were not for the fact that the stack of ...
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1answer
57 views

Work Done On a Body When It is Not in Contact with the agent of the Force

Is it necessary for work to be done on a body that the agent of the force remains in contact with the body? For example, if I hit a football with my foot with a small amount of force and it moves a ...
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50 views

Book recommendation [duplicate]

I already learned the Physics' basics like Newton Laws, Electricity, and Optics. Can you recommend me a good book for advancing with my learning of physics(with some math)?
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382 views

Ball rolling into a bowl - where is its maximum KE (speed)… given there is friction. See diagram

Please examine this diagram and answer the apparently trivial questions. I am particularly interested in reasoned answers for part (a)(ii) - where is the maximum Kinetic energy? I say it is at B ...
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1answer
2k views

Are the perpetual machines in this video really perpetual?

This video lists a number of perpetual motion machines that have been proposed throughout history: Robert Boyle's Self-Flowing Flask A "perpetual train" using rolling cones F. G. Woodward's hoop ...
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1k views

Example where angular momentum and angular velocity are not parallel

I am unable to visualize any case where angular momentum and angular velocity of an object are not parallel.
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586 views

How come a rigid body has 6 degrees of freedoms (DOFs) ? Isn't velocity a DOF?

For rigid body we need to know position of three points and their velocities to determine everything. So that would make 12 DOF. Why do text books say it has six DOFs?
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1answer
72 views

Spring with changing equilibrium

Suppose that we have two cars on a track, each with a different mass. Now suppose that the cars are connected with a spring. We smack one car. I would like to write down the equations of motion for ...
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1answer
74 views

Water level rise due to body in water

I recently came across a comment that when we push a rubber ball into water filled in a bucket, the water level rises because of the force applied by our hand (i.e. the more force we apply, the more ...
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1answer
100 views

How does a “hammer thrower” that we see in the Olympics, impart so much momentum

How does a "hammer thrower" that we see in the Olympics, build so much momentum into the club? It's sort of like the golf swing, the more momentum, primarily in the club head, the further the ball ...
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422 views

Friction forces and sliding slabs

I have 2 questions, one generalizing the other. Question 1: Suppose we have 2 slabs resting horizontally on a table. Assume there is friction between the 2 slabs as well as between the bottom slab ...
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172 views

At what angle do billiard balls scatter if they collide off center?

The angle defined by joining a line from the centers of the balls must be important. But do they follow this angle when viewed in the rest frame of one of the balls or in the CM frame? The spheres ...
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1answer
1k views

How is Mechanical advantage of Wedge = length of slope/width

Mechanical advantage is defined as Force Output/Force Input For a symmetrical wedge with the length of the slopes being equal and the width being the distance between the end points, articles quote ...
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4answers
129 views

Action and reaction - not the same effect

If I press on something, it presses me back with the same force. if I press a pillow with my fist, l do not feel pain but if I press a rock with my fist with the same force, I do feel the pain. ...
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276 views

Intuitive explanation of why orbits are closed?

Yesterday my brother asked me how orbits work. Suppose for the sake of the question that you are trying to put a rocket in orbit around the Earth. I explained that orbiting is essentially being in ...
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1answer
103 views

Landau Lifshitz energy for uniform rotation

Landau Lifshitz claim in their Mechanics book (39.11) that for a uniform rotation we have $ E = \frac{mv^2}{2} - \frac{m}{2} (\omega \times r)^2 + U,$ where the rotation is given by $v' = v + \omega ...
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56 views

How to produce a bigger rotational velocity from two rotational velocities?

If I have two electronic motors, both running at the same voltage and current, delivering the same rotational velocity, how could I produce a bigger rotational velocity from them?
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342 views

Verifying Newton's 2nd Law

Background/Experiment setup: In one of my classes a mass (0.04 kg) was hung from a pulley and attached to a much heavier mass (around 0.4 kg) that rest on an airtrack. A thread connected the hanging ...
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827 views

What is going on in the system? How are the formulas `mg sin(x)` and `mg cos(x)` derived?

When a load is resting on an inclined plane, there is force $mg \sin(x)$ that's vertical to the inclined plane and force $mg \cos(x)$ horizontal to the plane acting on it like this: My textbook ...