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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Case of the mysterious bullets (taken from Mad About Physics)

"Two ideal bullets, identical in shape, size and mass, strike the same target with the same speed just before the collision. Force meters at the target register two times the force value for bullet A ...
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Effect of movements of astronauts on International Space Station

I know that astronauts move in and around in ISS. When they move they also touch the modules of ISS and sometimes they apply force on the module to move. When this happens, as far as I know it affects ...
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24 views

Accelerating Tetrahedron [closed]

Four identical spheres are in contact with each other and form a tetrahedron. If acceleration of the top sphere is $a$, find the acceleration of the spheres on ground.
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1answer
59 views

Center of mass after explosion [closed]

How he treated the center of mass as if it is still in the same place , is not it supposed to change after explosion ? and is not explosion destroying the closed system? i mean it represents and ...
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2answers
73 views

Space Elevator: how would you keep the end of a Space Elevator's cable rigid?

I had a discussion with my wife about physics behind a Space Elevator. Imagine a cable rising 60k into the firmament for its elevator to climb. The cable would have to rotate in unison with the earth, ...
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1answer
91 views

Rolling a ball into a cone; what should the forces overall be?

This is my solution to finding angular displacement/velocity/acceleration on cone so far. Consider a cone, with an apex of half-angle $\psi$ pointing down, and a height of $h$. If I roll a ball into ...
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1answer
92 views

How did Newton establish his famous third law of motion?

For every action,there is equal and opposite reaction . This is the famous Newton's third law of motion. But how did he come to this conclusion? We can prove 2nd law using calculus. But how did Newton ...
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1answer
52 views

Non-deterministic particle system

This question is in the spirit of Norton's dome, an example of an apparently non-deterministic system in Newtonian mechanics. Under certain restrictions, the Picard–Lindelöf theorem guarantees the ...
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0answers
32 views

Plank stopping time (Continuation and Physical meaning)

A while back I asked this problem: "Plank stopping time" I thought it was solved, but now I have some questions about the solution. Problem: A plank of length $L$ and mass $m$ lies on a ...
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1answer
52 views

Simple Harmonic Motion homework [closed]

Suppose we have a rod of mass $m$ and length $l$ which is pivoted at center and two springs of spring constant $k$ are attached at opposite ends so that it performs simple Harmonic motion when ...
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0answers
114 views

Tension in a pulley system [closed]

In the question above, what I don't understand is how to calculate the tension in the second case (case in which the pulley is there). I realized after reading some questions, that the arrangement ...
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2answers
55 views

Pulling on a weakened rope - where will it tear?

Let's say I have a rope of 10m length and it is weakened in 3 spots: at 2.5m, at 5m and at 7.5m. Weakened means that if enough tension is applied it will tear at these points (all points are equally ...
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1answer
41 views

Can a Newtonian fluid have a non-linear speed distribution?

As far as I know, a Newtonian fluid follows the equation: $\frac{du}{dy}=\frac{\tau}{\mu}$ (where $u$ is $x$-axis speed and $y$ the height from the contact surface fluid-solid.) This leads to the ...
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0answers
21 views

Hovering jet-pack in rotating Toroidal Colony in presence of air

If we create artificial gravity by rotating large ring in space. Such as this Source: http://settlement.arc.nasa.gov/70sArtHiRes/70sArt/art.html I fly a jet-pack and hover above a certain spot , ...
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1answer
30 views

Big jump or small jumps?

To travel a certain distance s, is it more energy efficient to use one massive jump, or several small jumps? (First approach deleted, didn't make sense) This approach is probably a lot better. ...
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3answers
105 views

Is not force required to start each and every motion,uniform or non-uniform however they might be?

A body which is at rest will remain at rest; and a body which is in motion will continue motion in a straight line as long as no unbalanced force acts on it. This is Newton's 1st law of ...
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1answer
25 views

Confusion about horizonally projected body

DESCRIBED IN IMAGE CLEARLY In the text book, I got the initial velocity of x-component initial velocity Vxi, Vxi = Vi cos(0); (0 = zero) but what if it is like the picture i showed, first it was ...
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1answer
25 views

Centre of mass as a function of distance [closed]

I have searched it on Google and also visited the HyperPhysics website to find out but all they seem to offer world centre of mass of continuous and uniformly bodies.My school textbooks are of no help ...
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1answer
42 views

I am somewhat confused with the concept of force being equal to mass times acceleration

For example, let's say a car, weighing 1300kg (m=1300kg) is on cruise control, going at a constant 80km/h. That essentially ...
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1answer
69 views

Two masses on frictionless table with one string connecting both masses on ground and the other string [closed]

From Morin's Introduction to Classical Mechanics page 342: A solid cylinder of mass $m$ and radius $r$ lies flat on frictionless horizontal table, with a massless string running halfway around ...
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4answers
244 views

In which direction does a wall exert the reaction force if it is hit diagonally?

I am confused about action-reaction forces and inertia of moving objects. As an example, take a cricket ball a bowler throws to the pitch: Suppose the ball is about to drop in the pitch with ...
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1answer
49 views

Frequency of Oscillations about Circular Orbit [closed]

I'm trying to figure out the frequency of small oscillations about the basic circular path of a mass at the end of a spring, being spun around a table. I understand that the spring will stretch out a ...
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2answers
102 views

Relation between torque and moment of inertia

I have seen 2 formulas: $\tau = I \alpha$ and $\tau = I \dot\omega + \omega \times I \omega$. Which one shall I use in which case please? Also, am I right to think that $\alpha$ from the first formula ...
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0answers
58 views

How to show circular orbit as a precessing ellipse

A uniform distribution of dust in the solar system adds to the gravitational attraction of the sun on the planet an additional force linear in $r$ where m is the mass of the planet, k is a constant ...
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3answers
76 views

Where does the energy required to stop a moving body come from and go?

For a long time, I have been thinking about this: In order to stop a moving body, I have to apply impulse to change the existing momentum to $0$. For the impulse I have to impart force on the moving ...
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0answers
11 views

Question on a variant of Atwood machine with strings unwinding in one side

The figure is standard Atwood machine except that for the right object string tension acts on the left side of the object, and strings unwind from the object. No slip condition on a rolling ...
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1answer
50 views

Moment of inertia from torque and angular acceleration measurements

I tried to calculate the moment of inertia of a quadcopter along its roll axis using two different methods and the results do not match. Method 1: measuring the period of a bifilar pendulum, I obtain ...
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1answer
28 views

Wheel dynamics: reaction forces with ground

I am confused by part of a dynamic model in this paper: http://waset.org/publications/4405/real-time-control-of-a-two-wheeled-inverted-pendulum-mobile-robot see page 3, figure 5. All forces labeled ...
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1answer
18 views

belts and balls, correct size of holes

I'm working on a robot that has to transport a set of balls up at a 60 degrees angle. In order to do this I want to use a belt system with holes in it. Now my question is how big do these holes have ...
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1answer
76 views

How did Newton discover the universal law of gravitation?

I am having trouble comprehending how anyone could come up with this formula: $F = \frac{GMm}{d^2}$ Could someone walk me through this?
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2answers
49 views

How to take in to account torques applied at different points

Suppose we have a rigid body with known moment of inertia through some axis ($J$) and that there are multiple torques being applied in different points in that body. I know that for a rigid body, the ...
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2answers
80 views

Can we deviate a bullet from its target? Did anybody try this?

Can we deviate a bullet from its target? Means by applying any strong field at the target? Is there any technique so far like this!
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1answer
1k views

Are all machines linearly scalable?

For all machines (cars, elevators, computers, etc), when size, power requirements, dimensions are scaled by a constant N, will it work just as is? Will a car with all its parts 10x larger still work ...
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5answers
914 views

How does an object's motion behave if dropped from an aeroplane travelling diagonally upwards?

Imagine an aeroplane travelling with velocity $v$ at some angle $\alpha$ from East to North. A box is dropped from the aeroplane. What would the projectile of the box be? Would it be a parabola with ...
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3answers
928 views

Changing Rotation Direction in Mid Air

Not sure whether this is an appropriate question for this site, but could anyone explain the physics behind how this skier is able to change his direction of rotation mid-air? ...
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1answer
50 views

What is the net force acting on a climbing man by the rope?

I am confused with determining the net force on the climbing man below by the rope. My analysis is as follows. Let the tension be $T$. As both hands hold the rope then there are $T+T=2T$ upward acting ...
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1answer
28 views

Rotation/torque about a point mass on two linked rods

I have two rods with lengths $L_1$ and $L_2$, connected with a joint in the middle and I would like to express the moment(torque) around a point mass (P) at the far end of rod 1. The relation between ...
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2answers
119 views

Weight versus gravitational force [duplicate]

What is the difference between weight and gravitational force? I am a beginner who want to study physics properly.
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1answer
24 views

How to find the maximum height with a loss of 5 J of energy due to air drag [closed]

Can someone please help me to figure out how to use the 5J of energy into my equation for the maximum height. I know that the maximum height is given by, $$h_{max}={(v_f-v_i)^2 \over 2g}$$ but I'm ...
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3answers
57 views

Can a rigid body have three independent rotations, about three different, mutually perpendicular axes?

It appears that this is kinematically possible, but it looks quite unprobable. For example, it is quite improbable for a sphere to have rotation about three mutually perpendicular axes (supposedly ...
3
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2answers
209 views

Why does friction play the role of centripetal force during the turning of a car?

What makes frictional force the centripetal force of a car turning along a curve? As friction is the opposing force and acts anti-parallel so there is no component of frictional force towards the ...
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2answers
41 views

Who feel more impact of fall

A person jumping from a higher building is likely to suffer less injury than the person jumping from a short building as the person from large building fall long enough to attain drag force which ...
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3answers
68 views

Finding maximum height of projectile motion using potential/kinetic energy

I'm having some difficulty understanding how to find the maximum height using conservation of force. This is the picture I'm looking at: and this is how you find it: $$\begin{align*} ...
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2answers
74 views

If mass is added to a toy car does it affect its speed making it faster

If mass is added to a toy car (29.7g) and dropped down a wooden ramp would it affect its speed making it go faster? I know friction comes in to play to, so if you could give me an answer or an ...
4
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1answer
166 views

Why am I wrong about this dynamics question?

I disagree with the answer to this homework question. Here it goes. The coefficient of static friction is 0.60 between the two blocks in figure. The coefficient of kinetic friction between the ...
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2answers
202 views

Why did I get this dynamics question wrong? [closed]

I'm wondering as to why I got this physics question wrong, despite it being quite simple in nature. I believe that I missed something while working on the problem. Basically, the question involves ...
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3answers
728 views

Acceleration of an object dropped inside an accelerating elevator

A stone is released from an elevator going up with acceleration of $g/2$. What is the acceleration of the stone just after the release? The answer is $g$. Shouldn't the stone carry the acceleration ...
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1answer
50 views

What is the final velocity of a stone dropped out of a rising balloon? [closed]

A balloon is starting from the ground has been ascending vertically at uniform velocity for 4 sec and a stone let to fall from it reaches the ground in 6 sec. Find the velocity with which the stone ...
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2answers
110 views

Effect of steering a car at high speed

I take it the angle of the steering wheel in a car is roughly proportional to the curvature, and therefore inversely proportional to the turning radius. When I am driving slowly and want to turn the ...
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0answers
14 views

Sheer leg derrick tension in cable for equilibrium is not what it should be?

As you will note, the final solution of $5.79$ kN is not equal to that of $w$. Isn't this impossible? If there is no friction at point B and the cable is assumed to be massless, shouldn't the ...