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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Does the velocity vector always point in the same direction as the momentum vector?

I was told that the angular velocity vector does not always have to point in the same direction as the angular momentum vector. This is due to the fact that they are related by the equation $L=I ...
2
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1answer
21 views

Ball rolling on half-pipe

It is well-known that a ball rolling down a half-pipe where the side it starts on has enough friction for the ball to roll without slipping and on the side other to be frictionless, that the ball will ...
1
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1answer
31 views

Can Tension between two blocks on a horizontal plane be discovered in these conditions? [on hold]

the bodies are linked by an ideal string, one has m1=10kg & the other m2=20kg The force is known and is pulling horizontally, F=60N on the lighter object the coefficient of friction is said to be the ...
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1answer
38 views

Acceleration of Rain drop

Under the heading 'Points to remember',my textbook states: It is possible that an object can be increasing in speed when its acceleration is decreasing as in case of a raindrop. I could not get ...
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1answer
23 views

Finding time period of oscillations in a multiple spring system attached to a solid cylinder [on hold]

A solid cylinder of mass m and radius R is kept in equilibrium on horizontal rough surface. Three unstretched springs of spring constant k, 2k, 3k are attached to cylinder as shown in the figure. Find ...
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1answer
28 views

Determining the velocity function for a particle on a rough inclined plane

This is a problem from the problem book by IE Irodov (Problem 1.106). We have a rough inclined plane with coefficient of friction $\mu = \tan\alpha$. A particle is kept on the incline and projected ...
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0answers
27 views

Newtons 3rd law, on two opposing discs?

Assume a large disc at rest(bottom disc), and free to move. Above it is another disc(disc2) that's rotating, and a motor fixed on that large disc(bottom disc) as well, that's load is a disc rotating ...
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0answers
16 views

How to solve Kinematics: two objects meeting in the air

A water balloon is dropped from the top of a 200m high tower. An alert archer at the base of the tower sees the balloon being dropped, waits for 5s, then shoots an arrow at 40m/s straight up towards ...
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0answers
35 views

Circular motion and momentum

I have to explain why there is a force pointing inwards in a circular trajectory (assume constant speed), but without relying on centripetal force argument. So I choose two arbitrary points in the ...
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0answers
19 views

Time for water wave to reflect

In class we discussed an experiment for measuring the speed of waves in water. The basic procedure went something like this: Make a wave at the near end of the tank and wait for it to travel to the ...
1
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4answers
86 views

Gravitational force of a ring [on hold]

Given a ring with mass $m_1$, radius $R$ and a point mass $m_2$ with distance $x$ regarding the center of the ring. How can I calculate the gravitational force of this ring ? At first glance I'd say ...
22
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4answers
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Could I break the sound barrier using circular motion? (And potentially create a sonic boom?)

Ok, Lets say I get out my household vaccum cleaner, the typical RPM for a dyson vaccum cleaner reachers 104K RPM, Or 1.733K RPS. In theory, this disc would be travelling with a time period of ...
1
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1answer
37 views

Work done in raising a rope at constant kinetic energy?

Usually the question I had was work done in raising a rope at constant speed. Obviously as you raise the rope, the mass changes over time. It'll be a simple integral. But what about work done in ...
0
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3answers
54 views

Why is the total energy of an orbiting system negative?

Assume it's an circular orbit. Object A orbits around object B. Take object B as frame of reference. .$E=KE_a + GPE$ .$E=\frac 12m_av_a^2 +(-\frac {GM_bm_A}r)$ .$E=\frac 12m_a(GM_br)+(-\frac ...
-2
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1answer
44 views

quantum mechanics, lighting mechanics [on hold]

If we were able to place two square mirrors (each other with exactly the same size) perfectly aligned the one mirror facing the other, at a very very close distance that light could not interfere ...
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0answers
32 views

Relative kinematics and laws of Newton

I am an engineering student and currently taking a class on kinematics and dynamics. I study at a German university so it may be that I don't translate everything correctly. In the first module of ...
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2answers
59 views

Confusing, can a motor on a moving disc stop the disc?

I've been troubled trying to solve this problem. If a motor is fixed on a moving rotating disc and the motor's rotor has another disc attached to it. What would happen if we attached the motor's ...
4
votes
3answers
64 views

Walking on water

I was wondering about walking on water. I wonder if we can use surface tension to do this. Lets say I make a pair of shoes in shape which has infinite perimeter (e.g a koch snowflake) with glass. Now ...
0
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1answer
25 views

Weightlessness felt during roller coaster rides

Can someone explain the physics behind to why we feel weightless during roller coaster rides Please indicate how the forces act in a clothoid loop .
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0answers
67 views

Why did Feynman tell “we cannot locate earth's angular position, but we can tell that it is changing”?

I was reading "Symmetry in physics" by Feynman, where he wrote: If we perform sufficiently delicate experiments, we can tell that the earth is rotating, but not that it had rotated. In other ...
0
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1answer
24 views

What is total force in this context?

One site said the total forces is the sum of the vectors. My homework question is "A skydiver of mass 90 kg is falling with a terminal speed of 60 ms-1. What does that mean? What is the total force ...
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0answers
17 views

Energy spring problem [on hold]

Online homework question. A 270 g block is dropped onto a relaxed vertical spring that has a spring constant of k = 2.0 N/cm. The block becomes attached to the spring and compresses the spring 12 cm ...
0
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1answer
29 views

What's my $dM$? Gravitational Potential inside a circle of mass

I'm trying to find the gravitational potential for an arbitrary point within a ring of uniform mass density. The point is constrained to be in the same plane as the ring. So we start with: ...
1
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1answer
36 views

Angular velocity and instantaneous rotation axis

Let's suppose that we have a cylinder of moment of inertia $I$ rolling on the floor without sliding, moving with linear velocity $v$ and rotating around an axis passing through the center of mass with ...
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2answers
74 views

The Coefficient of Restitution of a bouncing ball

If I drop a ball from a height $H$ and the ball rebounds from the floor it will bounce back up to a height of $e^2h$ where $e$ is the coefficient of restitution of the collision between the floor and ...
0
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1answer
35 views

How to find an equation for $x$ in terms of $t$ for a particle falling under gravity with resistance given by $mkv^2$? [on hold]

Okay so I have determine the velocity $v$ and displacement $x$ as functions of $t$ for a particle falling under gravity with resistance given by $mkv^2$. I have set up the equation of motion divided ...
4
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3answers
60 views

Two questions about the coefficient of restitution

If you were to drop a ball onto a surface from a height $h$ and the ball collided with the surface and then rebounded, would the ball then travel a distance of $eh$ back up from the surface where $e$ ...
0
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3answers
68 views

How to find out how far a ball will travel after it's 3rd bounce?

Suppose I drop a ball from a height $H$ above a flat ground, how can I determine how far it will have traveled by the time the ball hits the ground for the 3rd time $L=x$?. I know how to calculate ...
0
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3answers
76 views

Why is the range of a projectile proportional to the square of the initial velocity?

I was watching the MIT lecture about projectile motion and the lecturer asked why $$D=\frac{(v_0)^2\sin(2\alpha)}{g}$$ Why is it $(V_0)^2$ not $V_0$? It is a hypothetical question i know that the ...
0
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1answer
29 views

Starting point for a derivation of fictitious forces

I came across this expression at the start of a derivation of fictitious forces: $$(dA/dt)_L = (dA/dt)_R + \omega \times A$$ Where the $L$ subscript refers to the laboratory (inertial) reference ...
2
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3answers
67 views

Moment Of Inertia About Centre of Mass

Why is moment of inertia minimum about centre of mass of any rigid body?
0
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1answer
34 views

Tension problem [on hold]

A weight "m" is suspended from the center of a light, taut and originally horizontal rope. After suspending the weight "m", what angle must the rope make with the horizontal if the tension in the ...
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1answer
72 views

Which physics quantities are real and which just a tool in the Newtonian apporach?

In the following question Is the change in kinetic energy of a particle frame independent? I presume change in K.E. means K.E. difference, $K(t')-K(t) $ as well as all frames are inertia In which ...
2
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1answer
32 views

Newton's Law in Integral form

Each of the Maxwell's equations has both an integral and differential form. Schroedinger's equation is a differential equation and, apparently (I haven't studied it yet), Feynman's path integrals are ...
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0answers
40 views

Why does ad^2 in moment of inertia doesn't cancel out? [on hold]

when you derive the translation formula for moment of inertia it is $Ix=(Ixx)-(Area)(DistanceCentroid)^2$ but when you use the trasnlation formula you use $Ixx = Ix+(Area)(DistanceCentroid)^2$... why ...
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0answers
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Galilean Relativity and Newton's Laws

Usually I see an inertial reference frame being defined as a reference frame in which Newton's first and second laws holds. That means that if a particle is at rest, it stays at rest unless some ...
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2answers
35 views

Use Work-KE Theorem? [closed]

I've been trying so long at this problem to no avail. I drew my free body diagram, but I'm unsure which formula to use. Could someone help me out?
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0answers
25 views

Collision of satellites [closed]

A satellite of mass $2m$ is in a circular orbit of radius $2R$ around the earth. By mistake, another satellite of mass $m$ is put in the same orbit and having opposite sense of rotation. The collision ...
2
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0answers
24 views

The athlete feels a centrifugal force when whirling the hammer - is there always a centrifugal force associated with a centripetal force? [closed]

(this is a homework question) To this, I would say that the centrifugal force is just the reactionary force of the centripetal force, which is causing the hammer to 'want' to move away. Therefore, ...
0
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0answers
22 views

Determining the direction of friction of a pole leaning on a block [closed]

This is the problem, can someone help me answer the item 7.40 thanks. The answer I get for the block to tip is 288 but the book said 353, how do you get 353?
0
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2answers
75 views

Homework question help [closed]

This is the homework question: When a springbok is startled, it will leap $2.5$ m into the air. solve for the time to rise $2.5$ m, taking $g$ as $10 \frac{m}{s^2}$. Knowing the time, ...
0
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3answers
90 views

Two balls travelling at different speeds collide in two referentials

In a referential R1, one ball B1 travels at 100 m/s and hits and another identitcal ball B2 that travels at 50 m/s in the same direction. Assuming the material in which the balls are made is such that ...
0
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1answer
33 views

Calculation of velocity via kinetic energy and momentum yielding different answer

I am attacking the given problem (as a preface I'm not asking to be spoon fed any answers, just looking for clarity from people much smarter than myself) A 15.0kg block is attached to a very light ...
1
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1answer
23 views

Comparing Brachistochrone curve with a Hypocycloid curve

I want to compare the time that it takes to slide a particle in a frictionless hypocycloid curve, so time would be given by the arclength divided by the velocity So I need first compute the ...
0
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2answers
34 views

Conceptual doubt about mechanic energy and two body problem [closed]

Suppose that two bodies are in plane, let's call the first m and the second M: In the first case m is moving in plane, so it has kinetic energy. M is attached at the origin (i.e not moving), so it ...
2
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1answer
27 views

Reaction to gyroscopic force

Just like the reaction of the weight of a body is a force acting on earth towards the body, where and in what direction does the reaction of a gyroscopic force act?
0
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1answer
79 views

Solve hanging rope question by using Lagrangian density [closed]

for this one, I can only do the first(a) $$V_{total}=\frac{mg}{l} \int_{x_0}^{d-x_0}{y(x)\sqrt{1+(\frac{dy(x)}{dx})^2}}dx$$ and have no idea about others.
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0answers
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A Tricky Rotational Equlibrium Question [closed]

READ THROUGH QUESTION 64.(page-373) I HAVE SOLVED THE FIRST PART AND THIRD PART. ...
0
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2answers
38 views

Force needed to hold a book between your hands - not sure about the influence of friction

I'm looking at this problem: A student presses a book between his hands, as the drawing indicates. The forces that he exerts on the front and back covers of the book are perpendicular to the ...
0
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1answer
43 views

Particle disintegration (Landau & Lifshitz)

In the particle disintegration problem in the book by Landau and Lifshit(z), it is considered a particle with velocity $\vec{V}$ in the lab frame, which disintegrates into two particles with masses ...