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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184 views

Infinite pulley system

http://www.physics.harvard.edu/uploads/files/undergrad/probweek/sol43.pdf Hi, I've been trying to solve this question for a while, I understand the first solution and also the solution to the second ...
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1answer
78 views

Second moment of area in parallel axis theorem

In parallel axis theorem why Ig second moment of area on axis passing through centre of gravity, is not zero. Even distance between axis and centre of gravity is zero.
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1answer
75 views

Difference between first newton's law and second newton's law ? [duplicate]

the first and second laws of newton are both similar, so why do we need the first law if it is the same as the second? what is the big difference between these?
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3answers
85 views

How would you explain the weight of an object in a lift accelerating up with acceleration a?

Observer in the lift:- He is unaware of his acceleration. He applies Newton's second law and got N = Mg. After that he used spring balance and found that the wait of the object is M(g+a). So to ...
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1answer
147 views

Conservation of mechanical energy isn't giving me the right answer? [closed]

I have been trying to solve this question: You are working for a shipping company. Your job is to stand at the bottom of an 8.0 m long ramp that is inclined at 37 degrees above the horizontal. You ...
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1answer
53 views

Why is the axis of rotation about O? (picture)

I'm not understanding part b. Why is the rotation about O? Shouldn't it be about C? If you do it about C you get a different answer because you'd get the same angular velocity but a different radius ...
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1answer
87 views

Conservation of energy and angular momentum

I'm writing a java program to simulate the solar system. All planets are modelled as point masses. How do I check if my solar system is conserving energy? I'm not sure how to calculate the energy of ...
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1answer
82 views
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1answer
63 views

Where to hit the pool ball such that it satisfies the given condition? [closed]

The question Where to hit the ball in such a way that after covering a certain distance it rolls back? You are given a pool ball and you have to find where to hit it such that it rolls back after ...
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2answers
138 views

Few questions related to Tension

I am struggling with the concept of tension in a rope. Below specific questions. I am understanding tension to be an elastic force between rope molecules. If so, is it fair to say the net tension ...
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2answers
55 views

Acceleration due to gravitational force [duplicate]

I need some help with below. So according to Newton's 2nd law, $a=F/m$, for a given mass, the acceleration depends on mass. But acceleration due to gravity is independent of mass. There seems some ...
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1answer
81 views

To what height does the ball rebound and what is the velocity of the struck block after impact? [closed]

Here is the problem. I have tried it four different times, and I will show my most recent work. [![enter image description here][3]][3]
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0answers
45 views

Pulley Friction

Why is the frictional force of a rotating pulley 0? For example, consider two masses and a string that links those masses passing through a pulley. Why do we not account for the frictional force of ...
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0answers
22 views

Am I exerting force when i am holding something? [duplicate]

So theoretically I found out that I am NOT exerting any force while I am holding something! Like Sir Isaac Newton said F=ma So technically it is true that when I hold something I am resisting it's ...
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2answers
47 views

Does force get divided among things?

If I exert a force to more than one thing at a time, will the force be divided among them or all of them will feel the same force? I mean imagine that I have tied up 3 bags of same mass with A rope ...
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1answer
69 views

Why does a top spin so well?

I know that the force of friction does not depend on surface area, but then why does a top spin better on a point rather than a region of larger surface area. For example, if I spin a top on it's ...
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1answer
34 views

Rigid Balls aligned along a line in vacuum

Recently I've been trying to visualize a situation where i have these really rigid identical balls aligned along a line so close to each other in vacuum.Now if I were to apply an impulsive force to ...
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1answer
117 views

Why $k/m$ in simple Harmonic motion equal $\omega^2$? [closed]

I've come across this thing in simple harmonic motion but never did I manage to find a reason why $k/m$ should equal $\omega^2$ and the theory behind it. People say it is done for convenience equating ...
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2answers
46 views

A drop falling in the condensed air

A drop is falling in humid air with air resistance equal $F_r = - \alpha v^2$. In $t = 0$ the drop is ideally spherical, $h$ above the ground, has mass $m_0$ and velocity $v_0 = 0$. What mass and ...
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1answer
68 views

Tension at different points of a string during vertical circular motion

For a vertical circular motion, its standard to solve for tension at the 4 common points on the circle (North, South, East, West) My question is: Is it possible to solve for tension at other ...
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0answers
45 views

What motion does this experience?

I have two Earths of $x$ distance away from each other. I place a spacecraft perpendicular to the centre of mass and the distance between the two Earths. If the Earths are fixed, then the spacecraft ...
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1answer
25 views

Coefficient of restitution belongs to kinetics and not to kinematics?Reason

The Coefficient of restitution is defined as $$e=\frac{v_2-v_1}{u_1-u_2}$$ $$v_2\to \text{final velocity body 2}$$ $$v_1\to \text{final vel of body 1}$$ $$u_1\to\text{initial vel of body 1}$$ $$u_2\...
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3answers
767 views

When does normal force equal to $mg$?

Can someone once and for all explain when does normal force equal to mg? I know for sure that when there is no friction, normal force will be equal to mg. But, i encountered some questions when there ...
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1answer
122 views

Work Done On Circular Motion

I am trying to find the total work done on a ball, $m=0.8kg$, tied to a rope of r=1.6m length and swung in a vertical circle. I understand the total work done by both the tension in the string and ...
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2answers
52 views

Rocket altitude [duplicate]

I have a model rocket I'm planning to launch. I heard from someone that you can calculate the altitude by timing the rocket from the time it takes off to the time it lands. Does anyone know how to do ...
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2answers
70 views

Why does the mass on the cart-pole have to fall?

Not sure if I am posting this question in the correct community, as it relates primarily to reinforcement learning. Apologies early on if this is not so. In reinforcement learning many algorithms ...
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2answers
180 views

Is the reaction force for a stone hitting a wall infinite?

Let us assume a rigid stone which moves in empty space with a constant speed of $v$. (Or in the air with no friction and drag or you can imagine a free fall with friction). This stone hits a rigid ...
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2answers
52 views

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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0answers
17 views

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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1answer
91 views

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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1answer
134 views

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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1answer
209 views

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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0answers
74 views

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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0answers
39 views

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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2answers
47 views

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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0answers
33 views

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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1answer
111 views

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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0answers
32 views

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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2answers
634 views

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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2answers
190 views

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 ...
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1answer
88 views

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 ...
2
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1answer
98 views

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 ...
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1answer
28 views

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 ...
1
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3answers
95 views

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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2answers
76 views

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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0answers
55 views

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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4answers
512 views

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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1answer
63 views

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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0answers
51 views

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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2answers
91 views

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.