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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Lagrangian of a coupled pendulum

I am trying to find the Lagrangian for a coupled pendulum: the two pendulums have the same characteristics (length $l$ and mass $m$) and are attached to the same roof at a distance $d$. In addition, ...
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4answers
79 views

Can a person in a car hitting the interior of the car move the car?

As I remember, on old day explanation, a person in a car hitting the interior of the car cannot move the car, because there is no action and reaction force between the car and ground. But I doubt the ...
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58 views

Skeptical of the “Cannon Shot Rule” [on hold]

What I consider a highly suspect figure was imparted to me today in a lecture and it very immediately did not sit well with me. To wit, this cannon shot rule (see here for a reproduction of the ...
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42 views

What is wrong with my formulas for a mathematical model of a double pendulum? [on hold]

I tried mathematics but I've had no response in a month. I wanted to create a computer simulation on Matlab, using a model for a pendulum from this study (A double pendulum model of tennis strokes. ...
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1answer
46 views

Does the force on the bottom piece of a hummingbird feeder depend on the height of the water in the reservoir?

Intuitively I would think that the more nectar you put into the reservoir the more weight it will put on the bottom piece (the tray that holds the open pool of nectar that the birds can feed out of). ...
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43 views

Rotation of rod [on hold]

A uniform rod of length "L" is free to move and rotate in gravity-free space . when an impulse is given to one end of the rod perpendicular to its length, its center of mass moves with velocity "V". ...
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6answers
4k views

Newton's 3rd law… hitting drywall (which I break) vs hitting a brick (which breaks me)?

According to the Third Newton's law of motion: For every action there is an equal and opposite reaction. So, I understand that if I hit a brick wall with $50\, \mathrm{lbs}$ of force, the ...
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3answers
88 views

What causes more damage, a head-on car crash at 30km/h or one car at 60km/h crashing into a stationary one?

Which will cause a greater impact? Two identical cars colliding head on (in opposite directions), each going at $30\;\mathrm{km/h}$ OR One car travelling at $60\;\mathrm{km/h}$ colliding into a ...
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15 views

a spring is stretched 10mm by a weight of 2.0N calculate the force constant k [on hold]

stretched 0.01metres weight of 2.0newtons calculate force constant k calculate the weight of an object that causes an extension of 80 millimetres
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3answers
599 views

Newton's Second Law Confusion [on hold]

I don't quite understand the relationship between an object's mass, acceleration and net force. For example, if a car was going to the right at a constant velocity or with no acceleration, does that ...
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1answer
34 views

Extinction level meteor effects on Earth's crust pending on the surface area upon impact

Would it be possible to have a extinction level meteor hit Earth depending on shape to actually create minimal damage if turned on its thinnest area rather than hitting flat? The meteor would enter ...
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2answers
52 views

Use of $g$ for centripetal acceleration

I have attached an image above including the question I'm unsure of (part B) In a nutshell, a satellite is orbiting Earth at the surface. Given is $g$ and the radius of the Earth. For part bi) the ...
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0answers
29 views

What will be the new moment of inertia? [on hold]

Let assume we have a sphere of radius $R$, and we can simply calculate the moment of inertia if we consider the axis is going through the center O. Let's cut a sphere small radius $r$ from the sphere ...
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0answers
42 views

High School Physics [on hold]

Two girls are standing on a bridge over a river. One girl falls freely and the other ties a rope to her legs. Both jump at the same time from the bridge. The length of the rope is more than the ...
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0answers
64 views

Why move from Special Relativity to General Relativity? [on hold]

The concept of relativity is simple. Why take Maxwell's equations to a new Special Relativity level with the unproven assumption that photons have no mass? All other physical data (momentum, affected ...
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1answer
37 views

basic question about work exercise [on hold]

I am learning independently from Tobochnik's statistical physics text. He asks a warm up question about work: A person pushes a block up a frictionless ramp. Is the work positive, negative, ...
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2answers
60 views

Question regarding elastic collisions and the conservation of momentum / energy [on hold]

I've been working on this question for a few hours and I cannot quite convince myself that my answer is correct. I've read the relevant section in my textbook, but I guess the lightbulb just isn't ...
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1answer
28 views

Force dependence on velocity : Drag

I just listened to the second lecture of Leonard Susskind on classical mechanics where he discussed that force can't be proportional to velocity, since it's unable to retro-dict (predict past). He ...
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0answers
19 views

Analysing kinetic energy in different frames [duplicate]

Case A: Say we observe a body X moving with a velocity of 30 on the +x and we(the observer) are stationary. Case B: The observer moves with a velocity of 50 on the -x. The body X is moving in the ...
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0answers
36 views

What really is force? [duplicate]

I know the second law of Newton says $F=ma$ which seems to me the most fundamental expression of the force. In other words, force cannot exist without a "forced" one. It is somehow a "secondary" being,...
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17 views

Simple harmonic motion [on hold]

A body executing shm has 10cm as amplitude and time period is 1.5s. Calculate the time taken by the body to travel a distance 5√3 cm from the mean position. I have used the formula x=asim(wt) And ...
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1answer
54 views

Velocity of satellite to crash into the earth

I was reading through this post today and was very impressed by the response that was given. However, what would have to happen to the velocity in order to collide with the Earth? Velocity of ...
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2answers
40 views

Does displacement affect force? [on hold]

I am sorry for being unclear with my previous question. The main topic of the experiment we conducted was about work. As we learned: $W = Fd$ Work, from my understanding, is the product of work and ...
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2answers
47 views

Work done by internal forces of a rigid body

I am reading Goldstein's Classical Mechanics book, and I came across that: In a rigid body the internal forces do no work Is this statement based on the assumption that the internal forces are ...
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0answers
11 views

How do rockets fly? [duplicate]

Is it that when a rocket loses its mass due to the escaping gases that results in its acceleration due to the same force acting upwards? If so, how is Newton's Third Law associated with it?
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24 views

Stuck with 2D kinetics problem [closed]

I've been trying to solve this exercise for the last four hours and I'm totally stuck. The problems goes like this: Given the mechanism in the image, located in the vertical plane, the OB cord ...
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2answers
33 views

Forces on body above body moving at constant velocity [closed]

Let's say the system is moving at constant velocity. What are the forces applied on B? Is there a static friction force? I find it hard to imagine what is happening to object B. $\Sigma F$ is $0$ on A ...
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1answer
38 views

understanding kinetic friction [closed]

I have a pen on my table. I apply force horizontally to my pen. The force I apply is stronger then the maximum static friction so it moves. I move the pen at constant velocity. Now if we look ...
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1answer
45 views

How do gravitational sling shots work? [duplicate]

How can an object move faster after leaving the gravity of a planet, should a gain in potential energy by moving away from the planet lead to a loss of kinetic energy? Or am I missing something ...
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0answers
24 views

Riemann Invariants

I understand that the Riemann Invariants for an expansion wave (isentropic) are constant along the particular characteristic line i.e.: $u + \frac{2c}{\gamma-1} = const $ along $dx/dt=u+a$ (1) ...
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1answer
46 views

In the following problem, where did $v_{cm}$ come from? [closed]

In the following problem, where did come from? I don't recall any formula that this equation could be derived from...?
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2answers
30 views

Setting up equations for a vertical spring-mass system [closed]

I am preparing for an exam in classical mechanics and today I have encountered a slight problem when solving a more complex spring-mass system. Consider the following setup: Then the system of ...
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0answers
45 views

Please tell me which of the Equation is wrong; the Angular momentum or the momentum? [closed]

(Sorry, it's not 2M. It's m+M) Two rigid body is fastened at a stick. A bullet collides into the first body and become one, and the stick rotates. When the bullet collides, there is no outer torque ...
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1answer
56 views

Conservation of enegry in case of Exploding Projectile [closed]

Consider the following problem : A projectile of mass M explodes, while in flight, into three fragments. One fragment of mass $m_1 =\frac12 M$ travels in the original direction of the projectile. ...
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0answers
37 views

All about Frictions. (Help me) [closed]

A 20-kg body is on a plane inclined at 60° from the horizontal. The coefficient of friction is 0.22. What force at 30° with the plane will cause the body to move upward at a uniform speed? 2.A block ...
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0answers
40 views

Friction and movement in a system with body above moving body in newtonian mechanics [closed]

I have a problem in analyzing movement with friction involved. I do not know how to correctly analyze systems as such and what is the correct view. I have tried to answer the several question below. ...
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0answers
30 views

Moment of Inertia of a curved part of a graph [closed]

How to find the moment of inertia of a curve about a given axis. For example : How can we find the MI of the curved part of :$$\sin x\ $$ EDIT: Assume the range from $$[0 ,2\pi ]$$ and the axis to ...
2
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0answers
90 views

Foucault pendulum, where did I go wrong?

I wanted to approximate the number $N$ of periodes needed, such that the foucault pendelum turns one time. Though my result is off by the factor 2 of the results I found. What I did: I assume the ...
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0answers
33 views

Dynamics of pendulum coupled to a gyroscope [closed]

We know the dynamics of a pendulum and we know the dynamics of a gyroscope. I put together the following I diagram below. The interesting thing as that the system has a beat frequency where the ...
10
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2answers
113 views

Can one rise through a free-falling rope?

I am a little confused about this question. I cannot imagine that it is possible to rise through a rope (assuming inextensible) that isn't fixed in its upper end. But when I solve this problem, I see ...
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1answer
28 views

Conservation of Energy with Rotation Caused by Friction

A book that I am using to study poses the following problem: Suppose you wish to use a spring with a force constant $k$ to launch a spherical ball or radius $r$ and mass $m$ up a ramp of inclination ...
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0answers
12 views

Newton's law - satellite position (in 2D) for specific moment of time [closed]

I’m trying designate function that calculate satellite position (2 dimensional) for specific moment of time for better understanding Newton's law of gravity. To verify my calculations I created second ...
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0answers
20 views

How to calculate the elapsed time to reach x? [duplicate]

Can some one provide a guideline about how to solve this problem?
0
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0answers
44 views

How to calculate the time for reaching 1/2 of the height for an object [closed]

I need to calculate the time for reaching the red object to the 1/2 of it's height. Can somebody provide me some guidelines?
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1answer
52 views

How would you go about solving this difficult physics problem? [closed]

I was able to calculate an angular frequency of 85.4357 rad/s for this mass. However, I am confused as to what to do next. Any ideas?
3
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2answers
58 views

How do I calculate a upward-pulling force on a swinging pendulum?

I'm trying to implement a simple pendulum using a 2d physics system that can model rigid bodies with gravity. The problem is that I don't know how to calculate the upward-pulling force of the rope, as ...
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1answer
85 views

Validity of Point Mass Approximation in Newton's Laws of Motion

Chapter 2 of Kleppner & Kolenkow's An Introduction to Mechanics reads as follows - Newton's Laws describe the behavior of point masses. In the case where the size of the body is small ...
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3answers
111 views

Why centripetal force does not increase the value of tangential velocity? [on hold]

I found in a text book that the value does not change because the centripetal force is perpendicular to the tangential velocity. But I am confused, because a vector can have a component, which is ...
2
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2answers
43 views

Why is $mg$ positive and $N$ negative in this problem?

In this problem: A car of mass $430\ \mathrm{kg}$ travels around a flat, circular race track of radius $178\ \mathrm{m}$. The coefficient of static friction between the wheels and the track is $0....
6
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4answers
141 views

Will a tennis ball go further if i hit it with the side of the racket?

If i hit a tennis ball 'properly' on the stringing, does it go further than if i rotate the racket 90 degrees in my hand and hit the ball with the same force, but on the side of the frame? I'm ...