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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Classical gravitational waves, again [duplicate]

I'm basically duplicating this question, because I'm not satisfied with the answer. Here's why I'm not satisfied. If we know that "gravity travels at a finite speed", then it seems obvious that it ...
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110 views

How to explain the force applied on this object? [closed]

Sorry for posting such a simple problem but I'm having trouble understanding this concept. In the picture below, we have a force, $ \vec F_{app}$ acting on two objects, A and B. Mass of block A: $ ...
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What Keeps a Pendulum Moving In a Circular Path?

From the figure, we know that $F_{net} = mg\sin\theta$. Now, this force $\vec{F_{net}}$ is in the direction of the velocity $\vec{v}$ of the bob, both are tangent to the path. Therefore, the net ...
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36 views

Particles velocities directly after an inelastic impact with a smooth frictionless surface

Let us consider the following situation where a dumbbell falls onto a smooth and frictionless surface. The dumbbell is formed of 2 particles, each of mass $m$, linked by a massless rod of length $...
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1answer
23 views

Kinetic Energy in the Center of Mass Frame

Given two bodies moving along a line, I can find the velocity of the center of mass frame. Taking the time derivative of the Galilean transformation I get $v'=v-v_{cm}$ By definition, the total ...
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1answer
71 views

Calculate constant acceleration needed to reach terminal velocity at specific time [closed]

I'm trying to find a way to calculate a constant acceleration given the following: One dimensional motion. The only forces involved are the force ($F_a$) caused by a constant acceleration ($a_c$) ...
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64 views

Can the constant $k$ from Kepler's third law be independent of the mass of the planet?

Consider Kepler's third law The square of the orbital period $\tau$ of a planet is directly proportional to the cube of the semi-major axis of its orbit $a$. $\frac{\tau^2}{a^3}=k$ The ...
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61 views

laws of motion while climbing a rope

I'm a little confused with the application of laws of motion on a man climbing a rope. Suppose a man of mass Mg is climbing a rope with an acceleration a. Rope is massless. Now if look through the ...
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Do all forms of energy fall under kinetic and potential energy?

I know that energy is recognized through motion. Even in the mass-energy equivalence a velocity is present even though it is a rest-energy (Not really sure if this would count as a potential energy ...
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0answers
43 views

Flow Rate in a tube with zero roughness [closed]

Assume the following setup. Given the Diameter of the pipe, difference in elevation (z1 - z2), pipe length, what would be the theoretical way of determining the flow rate (Q) within tube? Assume ...
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1answer
56 views

How was the concept of work-energy developed? [duplicate]

I doubt that the concept of work-energy was actually discovered this way. However in the algebra based physics book I am reading, work done by a constant net force is defined as $W = fcos \theta s$ ...
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Does a central force have to be independent of angle?

When defining a central force, some sources, like Wikipedia, say that the magnitude of the force only depends on the distance $r$: In classical mechanics, a central force on an object is a force ...
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41 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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34 views

Circular motion and car tire angle [closed]

I'm trying to figure out what angle to turn the front tires of my small robotic car (about a foot in length) so that it moves in a circle (on level ground) of radius r (will be accommodating circles ...
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0answers
55 views

The coffee ring effect

Would spin coating a homogeneous solution of colloids also result in a coffee ring structure? Or is it just naturally drop casted evaporation methods that lead to the same.
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39 views

Energy dissipation in spinning wheel

I was given the following question in a test. A spinning wheel A is brought in contact with an identical wheel spinning at identical speed.The wheels slow down under the action of friction.Which ...
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2answers
64 views

Mass required to prevent sign falling over with a set wind load - activity stations for disabled children

I'm currently working on my thesis and I'm stuck on a question. I'm designing activity stations for disabled children to be used for equine therapy. The stand is 9ft tall and I've calculated the the ...
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4answers
87 views

What is the Role of gravity?

I am new to physics and I understand gravity is a pulling force. Let's assume a ball has been placed on the ground. Does gravity has any role after I placed an object (e.g. ball) on ground? Sorry,...
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4answers
115 views

Ball dropped from train [closed]

A ball is dropped of a train traveling with high velocity, to a man standing near the track, the bank A) falls down vertically B) moves horizontally C) follows an elliptical path D) parabolic ...
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2answers
118 views

Does zero net force imply zero net torque?

I wonder, for a rigid body, if the vector sum of all external forces acting on it is equal to zero ($F_{\rm net} = 0$), does this imply that the vector sum of all external torques acting on it about ...
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1answer
150 views

The Physics Behind the American Death Triangle [closed]

I've heard a lot about the American Death Triangle and how it is awful for belaying. The Death Triangle is set up as such: you have two anchor points with a single rope or line running through both ...
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3answers
93 views

The force felt by a pilot when a package is dropped?

Here is a physics question that I wish to prove mathematically. A 100,000 kg aircraft drops a 1000 kg package of supplies over an arctic research station. What approximate force is felt by the 100 kg ...
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35 views

Rocket launch from equator

I am trying to simulate a rocket launch from the equator. I know that the earth's rotation around its axis will give the rocket an initial speed of $466$ m/s in the x axis. How much speed will the ...
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1answer
24 views

Can cyclic acceleration/deceleration be worse for fuel consumption?

Recently I have started to drive my car slower on the highway in order to save money on gas. However, I feel like I am spending at least as much fuel as before. One possible explanation that I thought ...
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2answers
47 views

Why is Torque Generated from Friction?

Why does a rolling ball get torque from friction. I understand torque in relation to lever arms and the force being perpendicular to said arm. But what about wheels? There is no lever arm so how is ...
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2answers
99 views

About reference frame in Newton's second law?

Classical physics models events occuring in the spacetime $\mathcal E\times \mathcal T$ where $\mathcal E$ is a dimension 3 euclidean point space and $\mathcal T$ is an interval of $(\mathbb R, <)$...
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39 views

Why can't we build a styrofoam 747?

What properties of materials explain why building the same structure at different scales requires materials of different densities and strengths? Consider an airliner, and flying models thereof at ...
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67 views

Confusion about Conservation of Mechanical Energy

I'm having a bit of difficulty understanding how to apply the idea of conservation of mechanical energy to a problem. One of the questions on my homework reads: A physics student shoves a 0.50-kg ...
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1answer
69 views

$P = h \rho g$ derivation

Here is a snapshot from my textbook : Here only three forces are calculated: The gravitational force The force due to the pressure $p$ on the bottom surface The force due to the pressure $p+\...
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1answer
34 views

Does a ball thrown down exert less force on the ground when we walk? [closed]

Scenario A: You stand still and throw a ball vertically down. When the ball hits the ground it exerts a specific force on the ground. Scenario B: While walking you throw a ball vertically down. When ...
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2answers
71 views

Find the relation between length of pulley and strings [closed]

A pulley is pulled with external force $F$. $x$ and $y$ denote the displacement of two ends of strings of the pulley and $z$ is the displacement of the pulley. Prove That $$z = \dfrac{x+y}{2}$$...
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2answers
110 views

Can torque relations actually be *derived* from Newton's Laws, or is it something extra?

For a long time I have wondered if there is a way to show that the rotational analogs of Newton's Laws are a direct consequence of just those laws, or are we adding more to them? I understand ...
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1answer
67 views

A simple explanation of Kepler's Third Law

Is there a simple way to explain how Kepler's third law follows from the inverse square law that of gravity (and laws of motion) For example for Kepler's second law we can say it's because Gravity ...
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28 views

Given Tension and the wave equation, how do you find the linear density?

I am given that the equation of a transverse wave of a string is y(x,t) = 2.00mm(sin(25.1rad/m)x-(415 rad/s)t) and the string is under 18 N of tension. From the tension, I got that the string is ...
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1answer
31 views

How can you calculate the thrust-to-weight ratio of a gun?

Is there some formula I can apply to the weight of a gun, along with the force of thrust it creates, and calculate if it will be able to lift itself off the ground or not? Without actually handling ...
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2answers
63 views

Why do tops move opposite to each other when colliding, not tangentially?

When two well-balanced tops collide, they tend to bounce directly away from each, in other words along the line connecting their centers. Intuitively I would expect the tops to move tangentially, not ...
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2answers
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Why was it difficult to walk in the same direction the train's acceleration, and easier the other way around?

The other day while I was walking in the same direction that the train was accelerating. Then I came across this question. Please if would answer it, I am very curious to know. But when I walked the ...
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79 views

Is Keplers First Law a consequence of the conservation of angular momentum?

It would seem that once you have deduced that the angular momentum is conserved then you can deduce: $r^2\dot{\theta}=h$ is constant Combining this with the radial equation of motion then yeilds a ...
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1answer
85 views

Range of ballistic missile on flat world

The range of the Trident 2 submarine-launched ballistic missile is stated to be at least twelve thousand kilometres - the exact figure is classified, but taking it as 12,000 km exactly for purposes of ...
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27 views

How can I get the Resonant Frequencies (Bode plot)? (Response of 2-DOF System)

I want to study the response of the system. I want to find the resonant frequency of the sprung mass (m1) and the resonant frequency of the unsprung mass (m2). Because I am not sure if I have ...
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3answers
120 views

Velocity of a body in a pulley problem involving a spring fixed to the ground

So the picture shows the whole situation. My question is, how do you find the velocity of the object after it had descended 10 cm (0.1 m) ? Pulley's radius 0.2 m, moment of inertia 0.2 kg/m I have ...
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1answer
120 views

Why does a force parallel to the axis of rotation do not produce torque? [closed]

One explanation can be that Torque is a cross-product (r x F). I want to know what is its physical interpretation.
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39 views

Rotation of join of two different rods when one is rotated [closed]

Two cylinders A and B made of same material and having same length of radii $r$ and $2r$ are soldered coaxially. The free end of A is clamped and the free end of B is twisted by an angle theta. The ...
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2answers
61 views

Vector addition forces with law of cosine

Given two vectors $\mathbf{F_1}, \mathbf{F_2}$ and an angle $\alpha$ between two vectors we can derive the resulting force $F_R:=\Vert \mathbf{F_R}\Vert$. $$F_R^2=\Vert\mathbf{F_2}-\mathbf{F_1}\Vert^...
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1answer
48 views

Change in energy during orbital decay

Suppose we have a planet orbiting a star and the planet radiates away some amount of energy $\Delta E$. I want to find by how much the orbit decays (i.e the change in orbital radius). One way to do ...
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2answers
43 views

Problem with transforming co-ordinates to rotating frame of reference

In the following question: A puck is placed on a friction less disk that is rotating with angular velocity $\vec \omega$. What is the equation of motion with respect to the rotating frame of the puck?...
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52 views

Conditions to impose for accelerations in systems of rotating pulleys [closed]

I do not understand completely how do rotating pulleys with ropes (that do not slip) work. Besides the equations of motions, which are clear to me, some conditions on the accelerations are needed to ...
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1answer
44 views

Does the centrifugal force affect stationary objects as seen from the inertial reference frame?

If an object is moving at the same speed as a rotating/accelerating frame of reference it's in contact with but in the opposite direction (making its displacement zero), would such an object be ...
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Toricelli's law of efflux in moving container

Suppose there is a big tank of water with a small hole near the bottom. Now if this tank starts moving with say a velocity 'v', then will Toricelli's law hold? I tried directly applying Bernoulli's ...
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1answer
36 views

What are internal forces and how do you calculate them?

There are many questions similar to the below, where you need to find the internal forces. I find such problems very poorly worded and designed. First, what do they mean by internal forces? Is it the ...