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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What does an $n$-body system with constant $T$ and $U$ look like?

Can someone give an example of a system where the kinetic $T$ and potential $U$ energy are constant (but not zero)? Here's what I have in mind: Say you have $n-1$ satellites of negligible mass ...
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33 views

What is the work done below proportional to? [closed]

A raindrop falls from a certain height to the ground, with a terminal velocity u. The viscous force is F = 6*3.14*n*r*v, where n is the coefficient of viscosity, r is the radius of the raindrop, and v ...
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1answer
58 views

Gravity and Mass

Two bodies of equal size and mass meet in space. My question is: will they attract each other equally or will their attraction cancel each other out?. Also: how long does it take for the two bodies ...
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1answer
83 views

Calculating force of a car [closed]

I'm simulating car cruise system and my results are not making any sense. I have been told that my force formula is wrong but I don’t understand why it is wrong and how I can fix this. Does anybody ...
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1answer
154 views

Hydraulic scissor jack lifting capacity

Can you please assist with a really simple question? I have a hydraulic scissor jack table with the following: 2 hydraulic cylinders, each with a cylinder stroke of 240mm, a cylinder bore of 50mm ...
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1answer
790 views

Moment of inertia of a cylinder about its base

I've tried to find the moment of inertia of a cylinder rotating about an axis parallel to its base (i.e about the 'End diameter') as one can see here . But when I checked my results with different ...
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2answers
96 views

Deriving spring oscilation period [duplicate]

We have a spring attached to a wall and at the other part an object on a frictionless surface. I tried to calculate the spring oscilation period. I used the conservation of energy and kinematics ...
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2answers
53 views

Determinate the right force intensity given a certain amount of energy to spend

I am using Chipmunk's physics engine to simulate 2D classical mechanics of solid polygons (excellent by the way!). The only way you can alter the spontaneous behaviour of the the simulated objects is ...
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2answers
82 views

Is it really okay to treat the Earth as stationary when doing free fall experiments?

Typical treatments of free-fall experiments treat the the Earth as fixed. Using this model, object being dropped moves toward Earth, but the Earth doesn't move toward the object. A more detailed ...
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968 views

How does friction and mass of the string influence the tension force?

According to my book, "tension is the reaction of a rope when it is stressed". Then it also said when the string is massless, tension is same everywhere. However in a,let, pulley-rope system,when ...
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137 views

What will be the acceleration of an object $A$ when its released by another object $B$ moving with an upward acceleration $a$?

What will be the acceleration of an object $A$ when its released by another object $B$ moving with an upward acceleration $a$? Will the acceleration of the object $A$ be more than the acceleration due ...
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359 views

Does a rotating plank only acquire rotational kinetic energy?

I have another doubt with a Kleppner problem :(. A thin plank of mass M and length l is pivoted at one end. The plank is released at 60$^{\circ}$ from the vertical. What is the magnitude and ...
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173 views

Does a spinning part affect the moment of inertia of a composite object?

I have been going back through some Kleppner problems and have a doubt concerning problem 6.18. It states: Find the period of a pendulum consisting of a disk of mass $M$ and radius $R$ fixed to ...
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1answer
85 views

Apparent weight on a hill and in a ditch [closed]

first time posting. I'm trying to solve these 2 problems. I have a solutions I just don't know if I'm right...seems odd that they are the same answer... 1) If you are driving over a hill of ...
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1answer
1k views

Calculate the weight that a hot air balloon can carry [closed]

Given a hot air balloon of radius 10 meters and negligible mass, calculate the maximum weight it can carry if the density of outside air is 1.2 $\frac{kg}{m^3}$ and the density of inside air is 0.9 ...
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1answer
105 views

Finding the minimum radius of the pivoted disc

Here is a question based on Simple Harmonic Motion that I tackled just now. However I think I am having an approach to tackle this but I am not sure about it. Ouestion: A uniform disc of radius ...
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1answer
317 views

Asymmetry of induced e.m.f due to a bar magnet falling through a coil

It is well known that as a bar magnet falls freely through a coil, an electromotive force is induced in the coil by Lenz's Law. However, it appears that the peak e.m.f induced (ignoring the ...
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1answer
229 views

Questions related to resonance/standing-waves and sound

I understand resonance for a simple harmonic oscillator but not for more complex systems like standing waves. How can I be in resonance with the normal mode in an organ pipe? I understand that the ...
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1answer
40 views

Difference between short impact and sustained pressure

If I press the wall (with my hand) I feel a little pressure at my hand and I move away from it. If I hit the wall (lets say using the same amount of energy for total work) I feel pain in my hand. ...
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48 views

(air pressure and displacement) Isn't this image wrong?

Isn't this figure wrong? P(x,t) = -B(dy/dx) . If the derivative of air displacement has a maximum, then this is where the pressure is minimum, not maximum as this figure suggests. Could someone ...
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43 views

Why is the change in height for mass be $2h$ in this question? [closed]

Could anyone tell me why the height is $2h$?, and is the total gpe in a system where the masses are balanced 0?
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1answer
364 views

wall thickness for a very large, low-pressure vessel?

I'm working on a space colony simulation, and I'm at the point where I need to calculate the thickness of the habitat walls, as a function of air pressure and geometry (and assuming some common ...
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2answers
113 views

Ballistic Pendulum Demo Problem

I have a question about the following problem: I got the solution $v=\frac{M+m}{m} \sqrt{2gh}$. But my real question is in the following picture: In the above slide, how can you derive ...
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1answer
266 views

Lift a weight with a pulley system

I have two weights, weighing one ten times the other. I should figure out a way to make a pulley system that can lift the heavier mass with the smaller one. I would like to use the least number of ...
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2answers
161 views

Why is work in a constant electric field equal to the force times distance?

Let's say, for example, that an infinite plate generates a constant electric field that exerts a force of 6N on a 1C charge. To move the charge from a distance of 5m to 1m from the plate, the work ...
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82 views

Initial conditions at Lagrange Points

I'm simulating the restricted three body problem. But I don't know how to found the initial conditions of the object located at the Lagrange points analytically or computationally. I mean my problem ...
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1answer
127 views

Force on a potentially rolling ball initially at rest

I'm a graduate student in mechatronics, but I give myself headaches on this astonishingly simple 2D problem. Imagine a ball (perfectly rigid) on an horizontal plane (perfectly rigid), initially at ...
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1answer
60 views

Spacecraft momentum question [closed]

Assume you're sitting in your spacecraft. The mass of you and the spacecraft is 2000 kg. You're traveling at 200km/h through the vacuum of space. You have a thruster pointing in the direction you're ...
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1answer
102 views

Lifting an Atwoods machine from the ground? [closed]

If we have an Atwood machine where masses $m_A$ and $m_B$ rest on the ground, then we apply an upwards force $F$ to the Atwoods machine. What is the acceleration of the blocks when $F=124N$, $m_A = ...
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1answer
215 views

Newtons third law and Atwood Machines, confusion about tension

The classic way of solving these problems is like so: $T = mg - ma$ and $T = mg + ma$. However, according to Newton's third law, is this not wrong? I know how to solve these problems, but the ...
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1answer
88 views

Curve of a rod bent by force on both sides

Suppose we have a flexible rod (i.e. it can be bent without breaking apart) and we excert a force on both sides, like this: If the force $F$ is not exactly horizontal, the rod will be bent and form ...
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2answers
59 views

Rocket towing an object

I'm not sure if my question makes sense, but I don't know where to start. A crate of mass $m_2$ is connected by a massless rope of constant length $l$ to a rocket of mass $m_1$. We take into account ...
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1answer
72 views

graphing velocity and time (v-t graph) [closed]

The question goes like this: If we push a body shortly uphill and it gets a starting velocity of $v \ ms^{-1}$,the coefficient of friction between the body and the surface is constant, represented by ...
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2answers
112 views

Understanding Momentum

I'm trying to learn more about momentum and I'm a little confused. Based on my understanding, in an isolated system, total momentum is conserved in a collision. Today in class the professor went over ...
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1answer
110 views

Consequences of inverse square law with vast distances (Gravity); (in addition, is light speed broken)? [duplicate]

As is well known, the gravitational force between two masses is dependent on the spatial distance between them. Therefore, even at vast distances, the masses exert equal and opposite forces on one ...
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2answers
127 views

What physical conditions would allow for this kind of perpetual seesaw

I'm working with a simulator(Box2D) and need to create these conditions. I have a perpetual seesaw with two objects on either side. I'd like for the following conditions to be met. The first ...
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1answer
142 views

The force on an infinite line of charge perpendicular to a on a rod of charge

Essentially the question is to calculate the force exerted by a charged rod perpendicular to an infinite line of charge: $\vec{F}_{\text{rod}\rightarrow \text{line}} =\dots$ My question is it okay to ...
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1answer
82 views

Question about pendulum

I came up with this problem by myself: How much force do I need to make a pendulum revolve? Now I imagined that the force $\vec{F}$ must be enough to make the pendulum swing until half of the ...
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1answer
80 views

Angular velocity of precession

So in my textbook they say this ${\rm d}\theta$ = |$d\vec{L}$|/|$\vec{L}$| $d\vec{L}$ is the change in angular momentum caused by a torque whose vector is perpendicular to $\vec{L}$, which is the ...
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1answer
208 views

Question about the parallel axis theorem

I've a question about the parallel axis theorem. So I'm perfectly OK with the derivation of the proof in 2D. However in the typical derivation they just say this in my textbook "Because the Zi ...
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2answers
305 views

Calculating the rate at which a car turns

This is going to be difficult to describe, as I have no real concept of this sort of physics, so please bear with me. If this is too much or beyond the scope of this website, I apologize. I am making ...
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1answer
35 views

Modulus of action-reaction forces

I read somewhere that action-reaction forces satisfy the form $$ \mathbf{F}_{12}=-\mathbf{F}_{21}=f(|P_1-P_2|)(P_1-P_2) $$ meaning that the modulus can only depend on the distance between the two ...
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1answer
264 views

Bullet hits block. Show that linear momentum is not conserved [closed]

"..." First, we will familiarize us with a collision between a homogeneous beam of length, $L$, mass $M$ attached with a frictionless hinge in point $O$ at one of the endpoints of the beam. The ...
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1answer
678 views

Truck moving uphill, object suspended from ceiling, determine acceleration [closed]

A truck is moving with constant acceleration $a$ up a hill that makes and angle $\phi$ with the horizontal. An object of mass $m$ is suspended from the ceiling of the truck by a light cord. If the ...
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1answer
56 views

Doing a spring experiment, and need to find the stretch required

I'm doing an experiment where I have to calculate the stretch of a spring needed for it to launch itself into a trashcan located some distance away. The spring is located on the edge of a ramp that is ...
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1answer
139 views

Balancing stick on hand - inverted pendulum motion

How do I calculate the velocity and acceleration of a stick that is vertically on my hand? How fast and far do I need to move my hand from side to side to keep balancing the stick? Assuming that we ...
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1answer
66 views

Two equations for $y$ in projectile motions

I have two equations on my equation sheet: $$y=v_o t \sin \theta - \frac{1}{2} g t^2.$$ $$y_{\max} = \frac{v_o^2 \sin^2\theta }{2g}.$$ I understand that the first one is an equation for the height ...
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487 views

Small Animal Terminal Velocity

I recently saw a cat fall probably 100 feet like in this video Cat Falls. It seemed as if the cat reached terminal velocity by the time it hit. Does this mean that cats (and other small animals) could ...
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1answer
102 views

Centrifugal force for non uniform circular motion [closed]

If a body is under non-uniform circular motion, will it experience or will there be any impact of centrifugal force on the body upon eliminating the centripetal force? update-sorry.the title of ...
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1answer
67 views

Static friction

Just a quick question, When a force on an object is equal to its static coefficient * normal force , would the object move or would it stay stationary? Or does the force always need to be greater ...