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.

learn more… | top users | synonyms (3)

3
votes
4answers
845 views

Is the work done walking up an escalator in the same speed and opposite direction of the escalator zero?

Work equals force times distance, but what about walking up an escalator in the same speed and opposite direction of the escalator? In the frame of the ground, the distance is zero so the work must ...
1
vote
1answer
175 views

How to observe Newton's third law violation? [duplicate]

I met a statement, that Lorentz force disobeys the third Newton's law. Is this true? Also I met some setups, where it was stated, that third law is violated. Also I met some explanations about WHY ...
0
votes
3answers
66 views

Work power and energy

When you push your bicycle up on an inclined the potential energy of the bicycle and yourself increases. Where does this energy come from?
1
vote
3answers
115 views

How is it that Force = Mass $\times$ Length / Time ^2?

I understand how $F=ma$ but what I am looking for is a diagram, idiom or concept that explains how force can be explained (in a partial layman's terms) as a combination of the dimensions; Length, Mass ...
0
votes
3answers
146 views

Newton's first law: unclear multiple choice question

Everyone knows that a body with no external forces acting on it remains at rest or moves with a constant velocity. But how would you answer the following multiple choice question: Question: A body ...
1
vote
1answer
36 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 ...
2
votes
3answers
318 views

Car “oomph”: power or torque?

Two of the most important magnitudes that characterize a car's engine are maximum power and maximum torque. How are those two magnitudes related to the sensation that the car has "oomph" or is ...
1
vote
0answers
54 views

Why is it harder to flip my cell phone about one axis than the other two? [duplicate]

There are three ways (three differenent axis about which) I can flip my cell phone - over the front (like a frontflip), about the center (like a disc of pizza dough being spun by a baker), and over ...
0
votes
0answers
28 views

Lovely flow rate [duplicate]

How can we calculate the measure of the air flow rate when it is coming out of the balloon? (I mean that which parameter affects that? For example, the measure of balloons neck or the ratios or ...
1
vote
0answers
56 views

How much energy does it take to hold a bag? [duplicate]

I'm holding a bag with some mass $m$. The force required for not letting it fall is equal to its weight $m \cdot g_L$ (where $g_L$ is the local gravity, assuming Earth this is $\approx 9.8 \; \text{m} ...
0
votes
1answer
58 views

Finding the centripetal force at any random point in a wheel which is rotating as well as translating

If we have a wheel which is decelerating due to friction with acceleration $-A$ and angular acceleration $-\alpha$, and we want to find the acceleration at any point, then we can simply find it using ...
2
votes
2answers
89 views

Has this double-slit experiment been performed?

A weak, single photon, source is controlled by a fast shutter and directs photons toward a double-slit. Quite far beyond the slits, compared to shutter speed, is the photon detector (perhaps a film). ...
1
vote
1answer
476 views

Kinetic energy of an expanding sphere [duplicate]

In the study of Newtonian stellar structure, Weinberg (1972) writes The uniform dilation of a sphere with uniform density will give it a kinetic energy $$U=\frac{3}{10}M\dot R^2$$ I don't ...
2
votes
1answer
50 views

Ball's opposite rotation caused by friction

Assume that you push a ball like in the picture (along the red line) with your hand with a some force. The ball will move forward while its rotating in this way: And after some movement, the ball ...
-6
votes
1answer
36 views

Replace the force system with a single force [closed]

Please I need a quick answer I have an exam tomorrow
-1
votes
2answers
60 views

Can anyone kindly help me with these sign conventions?

Since I have some confusions with the sign conventions , I have finally drawn up the following conclusions . Plz check if the following are correct .... ( I have taken all motions directed upwards as ...
0
votes
1answer
38 views

Rolling on a frictionless pond

I have a doubt about one of the questions in my textbook. Q- You are standing with your bag in your hands in the middle of a friction-less pond. How can you come out of the ice? There is of ...
-1
votes
1answer
47 views

Statics question: Calculate thrust force [closed]

First and foremost can someone explain what is being asked here please?
3
votes
4answers
160 views

What starts the conversion between GPE and KE?

When researching GPE and KE conversion, lots of websites say that as an object with GPE (Gravitational Potential Energy) falls, that GPE is converted into KE (Kinetic Energy), so there is less GPE and ...
0
votes
2answers
253 views

3D frame stiffness matrix local to global

I am working on a simple script to be able to solve frame structure using direct stiffness method. I am having following stiffness matrix for 2 node frame element: What is the correct way of ...
0
votes
2answers
81 views

Integrate the law of universal gravitation to get position [closed]

I'm trying to write Physics simulation software which simulates gravitational and electric forces between $n$ bodies. I know how constant acceleration is integrated to get distance, but I have no ...
0
votes
2answers
92 views

How does gravitational potential energy increase, if field decreases as $h$ increases?

(In the following constants are ommitted) Let $ M = 50, m = 5, h = 5$. Then $$ \text{Potential Energy} = \frac{50\cdot5}{5} = 50.$$ While after increasing the height $h$: $ M = 50 , m =5, h =10 ...
0
votes
1answer
107 views

Conservation of energy during rolling without slipping?

Say there's a cylinder laying on a flat surface, and the surface is rested on frictionless ice. Attached to the surface is an engine that is attached via a string to the center of the cylinder, and ...
2
votes
0answers
55 views

Rod rotated by elastic string [closed]

A uniform rod $AB$ of length 2m and mass 1kg, has a mass of 1kg attached at $B$. It can rotate freely about a horizontal axis through $A$. The end $B$ is attached by means of a light elastic string ...
4
votes
1answer
65 views

Is ordering players by height beneficial in a game of tug of war?

This can be considered a follow-up turn-around question for this similar question. I recently came across this interesting analysis of the game of tug of war. One of the closing discussions is the ...
0
votes
1answer
64 views

Does Newton's 3rd Law apply to friction?

Supposed body A slides on a surface. The will be a kinetic friction that acts on body A and opposite its relative motion. However, is there a kinetic friction that acts on the surface too i.e. the ...
2
votes
0answers
85 views

Modelling an Inelastic Collision

I've attempted to model the inelastic collision between a moving mass and a large stationary object, e.g. dropping an ball on the floor, for analysing the approximate kinematics and heat dissipation ...
0
votes
1answer
125 views

Thought Experiment: An object falling indefinitely under gravity?

So the other day, I devised this thought experiment: Consider an infinite tunnel, and you drop a coin of mass $m$ into it. Considering the effect of gravity to be applicable and neglecting air ...
-1
votes
1answer
61 views

Does a projectile always meet a freely falling body when aimed at it? [closed]

When we aim a projectile at a freely falling body why does it always meet it irrespective of the range and speed.
1
vote
3answers
61 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 ...
-2
votes
1answer
95 views

Could you please help me find another example of motion under null net force? [closed]

There are many familiar situations in which the net force on a body is zero and yet the body moves with a constant velocity. Here is one example: A car traveling at constant speed on a ...
1
vote
0answers
123 views

Calculating the torque required to move a heavy object (the calculations)

I wanna choose a motor for my bicycle and turn it into an electric one. So the physics part shoots. The force (Force=Mass x acceleration) that i will exert on earth surface(weight) will be my ...
4
votes
4answers
199 views

Kinetic energy of the object, but Potential energy of the system: Why is it so?

Examples from Principles of Physics (by Walker,Resnick,Halliday) will say it better: Let us throw a tomato upward. . .as the tomato rises, the work $\mathbf{W_g}$ done on the tomato by the ...
3
votes
2answers
244 views

What factors influence the spring constant?

For certain springs we have been taught that Hookes law, $F=-kx$ works. For such springs, what factors determine k. For instance, k is proportional to length. Can k be expressed in terms of ...
1
vote
3answers
93 views

A problem related to Work done by falling bodies : Expert's attention much needed! [closed]

I'm having a lot of trouble with this question, that I've found in my textbook. I've solved it in my own way and it's very simple! But the solution in the book is totally different. It doesn't make ...
4
votes
2answers
57 views

Confusion with potential in simple pendulum

I'm a maths student taking a course in classical mechanics and I'm having some confusion with the definition of a potential. If we consider a simple pendulum then the forces acting on the end are ...
1
vote
0answers
38 views

Velocity of ball after collision [closed]

I have a question regarding impulse. Suppose at a certain point of time ball has velocity $\mathbf{v}\cos\theta$ in horizontal direction and $\mathbf{v}\sin\theta$ in vertical direction (downwards) ...
14
votes
6answers
4k views

Throwing an object around the Earth. Is it possible?

Some of you might be familiar with the cartoon called Astérix. In one of the episodes, Obelix (the really strong fat guy in the stylish striped pants) enters a spear throwing competition. He beats the ...
-1
votes
2answers
59 views

Traveling to Mars in 24 Days

I am trying to calculate an electromagnetic rail launch from the Moon but I need to know if humans can survive the launch. Please see the specs below. 150 miles of track Proposed final launch speed ...
0
votes
1answer
30 views

A question on tangential and centripetal accelerations?

What is the proof that the component of acceleration perpendicular to motion for all motion is $v^2/r$, where r is the radius of curvature? Also, what is the proof that the component of acceleration ...
1
vote
1answer
27 views

Problem on bending plates in Newtonian Mechanics?

I am reading a book on interesting physics problems and demonstrations. One of the problems in the section on buildings, structures and equilibrium talks about a plate with one side attached to the ...
1
vote
1answer
30 views

Is the buoyant force on an object is the reaction force?

Is the buoyant force on an object is the reaction force for the force exerted by the objects on the fluid (newtons third law)? Or there are two sets of action reaction force? (objects force and ...
0
votes
1answer
83 views

Lagrangian mechanics and initial conditions vs boundary conditions

It bothers me that many basic books on the classical mechanics don't discuss the following difference between "Newton's laws" and the "Principle of stationary action". Newton's laws can predict the ...
0
votes
1answer
45 views

Equation for Figuring out the Displacement for a Projectile at an Angle

I'm wondering if anybody can simply tell me if there is a simple formula to solve for displacement when you've been given the launch angle and initial velocity? See; http://is.gd/LpT1EA To some, it ...
1
vote
1answer
52 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 ...
0
votes
0answers
10 views

dynamics: force, pulley, person in elevator [duplicate]

An 30-kg person standing on a 60-kg elevator suspended by a rope passing over a stationary pulley that is free to rotate. The other end of the rope is held by the person. The masses of the rope and ...
4
votes
1answer
86 views

Uniqueness of the equivalence class of inertial frames

Let us define an inertial frame as a frame of reference where the laws of physics take their usual form, as opposed to non intertial frames where one has to introduce pseudo-forces. We can further ...
0
votes
0answers
81 views

Two cars colliding with different speeds

If I have one car travelling at 30 m/s and another travelling at 10 m/s both weighing the same amount, why is it that the car travelling 10 m/s would have more damage? According to Newton's third law ...
1
vote
1answer
33 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 ...
0
votes
4answers
109 views

Absolute (as opposed to relative) concept of inertial frame

In mechanics there is a relative concept of "inertial frame": frame A is inertial with respect to frame B if A moves uniformly with respect B. That concept is easy to understand. There also seems to ...