# Tagged Questions

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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### Is Buoyant force a reaction?

When we fall on water. The surface molecules are pushed down and as a consequence molecules below the surface molecules and molecules beneath them and so on are also pushed down. Some of them are ...
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### Motion in Spaces [duplicate]

How does a shuttle move in the space as, the whole mechanism of a rocket is based on 3rd law of newton but, we can not apply 3rd law of newton in space because there is no reactive force in space?
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### Would an object falling on the surface of the Sun look like this? [closed]

I've been playing around with some rustic animation and then I came to simulating gravity over squishy objects, I simulated a squishy ball of unknown "squishiness" (I'm sorry I don't know a lot of ...
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### Explain this contradiction of violation of “ energy conservation ” using classical mechanics

Consider a rocket moves upward with some acceleration for a very small time say '$dt$' then the kinetic energy increases (for acceleration). as well as as the potential energy increases (due to height ...
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### Object Falling on spring

This is problem #23 from the 2015 F=ma contest: A 2.0 kg object falls from rest a distance of 5.0 meters onto a 6.0 kg object that is supported by a vertical massless spring with spring constant k ...
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### Conservation of Angular Momentum…or not?

This is my first post on physics stack exchange, but I thought the question was more appropriate than on that of math.stack. I'm currently designing a crude model of the sun-earth orbit (which I have ...
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### Why is normal force at a different location than its action forces (ie, seesaw)?

It seems very counterintuitive that the forces at the two ends also constitute the normal force at the pivot point. Does this principle apply even if the plank is tilted? (It would be good someone ...
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### Friction in an ascending elevator

When a lift moves up the normal reaction,R is greater than the weight,mg,producing common acceleration mf such that R-mg=mf Friction,F=coefficient of friction ×R.In case of an ascending lift R is ...
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### Storm in a teacup

The Beaufort scale defines storm as 24.5–28.4 m/s. Undoubtedly can you push air into a teacup at 26 m/s, but will anything (tea or otherwise) then remain in the teacup? In other words: Is it possible ...
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### Measure ball's acceleration down inclined plane

If I am asked to devise an experiment to find an expression for the acceleration of a uniform sphere (ball bearing) rolling down an inclined plane, as a function of the angle of incline. Hence deduce ...
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### What is exactly gravitational potential energy and explain P.E. $= -GMm/r$? [duplicate]

I was studying gravity and I came to know about $P.E.= -\frac{GMm}{r}$ which is derived by $GMm(\frac{1}{\infty} - \frac{1}{r})$ which the work done by the body to displace it from infinity to $r$. ...
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### How many Gs are my clothes experiencing in my washer? [closed]

During a spin cycle I got curious: How many Gs are at play in my simple washing machine? We can assume the drum is 50 cm wide and spins at 1500 rpm.
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### Does Newtonian physics work on a galactic scale?

I'm currently working on a simulation that aims to use Newton's Law of Gravitation to simulate how a galaxy behaves gravitationally. While I haven't gotten the simulation finished yet, I have had a ...
1answer
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### Modeling a pool ball rolling and slipping given initial velocity

I am trying to model a pool game. Currently my physics is faked by giving it an initial velocity and just subtracting from it every second. To make it more realistic I want to use physics to determine ...
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### When are energy, mechanical energy, momentum, and angular momentum conserved?

I am in AP Physics and my only real hangup is knowing when the said quantities are conserved. Please define what is the SYSTEM in your answer. I kind of have the basic idea. For example, if there ...
1answer
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### One block of pulley system collides with the ground [closed]

Question:- My attempt: Since the P block is given a velocity v in the downward direction, the Q block will move in the opposite direction(upwards) with the same velocity v. When the P block ...
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### Violation of newton's third law in case of fluids

If a steel ball hits an iron surface it bounces back due to the Newton's third law of motion. Then why does'nt it bounce back when it hits a water surface ? or for that matter even air ? The ...
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### Experimentally measuring a sphere's moment of inertia

I'm a freshman in Physics and I'd like to design an experiment to measure a sphere's moment of inertia except, well, I'm not very familiar with the concept beyond the formulas it comes with as it was ...
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### Deriving Kepler's First Law from Newton's Law of Universal Gravitation: Interpretation of the $u = 1/r$ change of variable

I'm working through a somewhat unsatisfying derivation of Kepler's First Law from Newton's Law of Universal Gravitation. The key to obtaining the equation of motion that you can solve lies in making ...
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### Gravity between two unequal masses. Do both masses move?

I've been watching videos about gravity and I have a question My understanding is that mass have gravity and gravity is a force which attract other object with mass. For example, I jump up and the ...
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### What is the physics (not math) of pseudo forces?

I have seen the mathematical concept of the pseudo force exerted to a mass in a non-inertial reference frame. But I did't find any theoretical idea that explains it. When I read the books, it says "to ...
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### Hammer will fall faster than the feather on the moon. 10 second thought experiment! [duplicate]

Please explain where my logic is wrong. a) Ignoring air, the same bowling ball will fall faster on Earth than on the Moon. b) Now, for the feather and hammer on the Moon, reverse your point of view ...
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### Given force as function of position, find the total energy as function of time [closed]

Given that the force for a non-linear spring connected to a mass $m$ sitting on a table is $$f(x) = -kx -ax^3,$$ Find the total energy as a function of time $E(t)$. I have no clue where to begin.
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### 2 men support a uniform horizontal beam at its 2 ends .If one of them lets go ,the force exerted by the beam on the other man will?

A) remain unaffected B) increase C) decrease D) become unequal to the force exterted by him on the beam This was a question in one of my books for mechanics, they solved the question using ...
4answers
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### Is Newton's second law tautologous? [duplicate]

Newton's second law $$\mathbf{F} = m\mathbf{a}$$ where $\mathbf{F}$ is the force, $m$ the mass, and $\mathbf{a}$ the acceleration, seems at first blush to be a simple tautology, since $\mathbf{F}$ ...
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### Where does the spring's energy go?

I have learned that ideal spring has no mass. Suppose, I attach a ideal spring (spring constant $K$) to a wall and pull it a distance $x$ it will have a potential energy $U = \frac{1}{2}Kx^2$ and if I ...
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### Sliding and rolling friction

I heard that friction depends only on the normal force but not on the contact area. Let's take a cube and a sphere which are of same weight (then normal force will also same ) but the force needed to ...
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### One formula that will include these all given properties

What is the maximum velocity of a car with mass m going on a road turn of radius R for it not to departure the road
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### Pressure generated by a molecule inside an enclosure

I want to find the pressure generated by a molecule of mass $m$ and speed $v$ that is alone in an enclosure having the volume $V$. I wander if I can use the relation: $PV=mv^2/2$
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### Calculating constant velocity from friction [closed]

I'm unsure if my Book is wrong. Either way, we send a pinball through a cylinder filled with oil, the forces that apply are. Fpinball = 15,8 ∙ 10^−6 ∙ 9,82 = 5,69 ∙ 10^−5N Foil = 𝜌 ∙ 𝑔 ∙ 𝑉 = 0,...
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### Question about spring force and work [closed]

An ideal massless spring can be compressed $2.33\ \mathrm{cm}$ by a force of $268\ \mathrm{N}$. A block of mass $m=3.18\ \mathrm{kg}$ is released from rest at the top of a frictionless incline of ...
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### Explaining conservation of angular momentum with a disconnect

A probe is rotating in space and an instrument comes loose and disconnects. I need to explain why the angular velocity $\omega$ of the probe does not change. This equation describes how the angular ...
1answer
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### Relation between force and torque for a set of gears/bicycle

If there are 2 gears meshed together and they are of different sizes, then rotating the smaller one will make the larger one spin with a smaller angular velocity but with more torque. And the opposite ...
1answer
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### Boundary behaviour of a mechanical wave

Let us assume we have a taut rope and I introduce a pulse in it by whipping one end. Now if instead of a clamp, I have tied the other end of the rope to a denser rope, a part of the energy is ...
1answer
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### An intuitive explanation regarding propagation of mechanical waves

I was studying mechanical waves today and have questions regarding how a pulse is propagated on a string and its reflection and transmission at a boundary and I hope I can find help here. First, ...
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### How does a cyclist moves the center of mass of the cycle-cyclist system?

Consider the image shown below, In the left diagram the centre of mass of the system lies upon the perpendicular from the point of contact. But in the right diagram the centre of mass has shifted ...
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### What is the difference when we measure torque/angular momentum about a point and about an axis?

When do we measure torque about an axis and when do we measure torque about a point?Whats the difference? I tried searching this on google but did not get satisfactory answer.
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### Why do linear momentum and angular momentum have to be conserved in ground frame only?

According the Newton's second law of translational and rotational motion respectively if the net external force /torque acting on a body is zero then the linear/angluar momentum is a constant . So ...
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### If a bullet were to hit a target point blank, would the force upon impact be the same force as the recoil?

When a bullet fires from a gun the force exerted on the bullet by the blast is equal and opposite to what you feel as the recoil. I know that acceleration on both the gun and bullet is different due ...
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### Rotation of a cube around its diagonal axis

I have the following multiple choice question that I am attempting to answer: For B1.3, (a) appears to be the most logical choice. It is my understanding that an object whose shape is asymmetric ...
2answers
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### Angular momentum about a moving axis

How can we define angular momentum of a system about an axis that moves parallel to itself? For example Axis passing through CM that is perpendicular to plane of body. When we talk about ...
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### What is required for a time-varying moment of inertia matrix?

Let me preface this question by stating that I am familiar with euler's equations for rigid body dynamics, torque and angular momentum. Despite the math, I'm still a little fuzzy about certain ...
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### What happens if a motorcycle going at 50mph crashes head into a car going at 60mph? [closed]

I wonder if a motorcycle (going at 50mph) crashes into a car (going 60mph), what is the damage that motorcycle will experience? Here's a diagram that shows what I've in mind: ...
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### How to show that the configuration space of two beads on a rod is a triangle?

I do math, and this problem showed up in the setting of translation surfaces. Lets say we have two beads of masses $m_1$ and $m_2$ on a rod of length $a$, with $m_1$ on the left of $m_2$. Denote ...
1answer
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### circular motion relative velocity question

You are standing in the middle of a disk of radius $2\:\mathrm{m}$ rotating at $\pi\:\mathrm{rad s^{-1}}$, and there's a smooth puck at $1.5\:\mathrm{m}$ away from the centre. If the puck was released,...