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 it really okay to treat the Earth as stationary when doing free fall experiments?

Typical treatments of free-fall experiments treat the the Earth as fixed. Using this model, object being dropped moves toward Earth, but the Earth doesn't move toward the object. A more detailed ...
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1answer
42 views

How does friction and mass of the string influence the tension force?

According to my book, "tension is the reaction of a rope when it is stressed". Then it also said when the string is massless, tension is same everywhere. However in a,let, pulley-rope system,when ...
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25 views

Potential Energy and Kinetic Energy [on hold]

how does potential energy related to height? how does kinetic energy related to velocity? how does potential energy related to those kinetic energy? how does potential energy and kinetic energy ...
2
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1answer
37 views

Gas pressure and centrifugal force

I think about a rotating torus (simplified tire) filled with ideal gas. Mass of gas is $m$ and molar mass is $M$. Pressure in non rotating torus is $p_0$. Temperature is constant $T$. Inner radius of ...
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1answer
21 views

Impulse on adjacent objects

Let's say two objects are sitting adjacent (in contact) to each other. If we start pushing one of them, we know that both the objects move, remaining in contact to each other. But let's now consider ...
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1answer
37 views

How does acceleration affect the orbit?

I want to know what roughly happens if we hit an orbiting body a little. And how is it possible that most of the objects have seemingly circular orbits around. How do they stabilize? I ask because it ...
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2answers
41 views

Can friction be brought in to zero value by means of laboratory experiments?

By newton's first law, an object will continue to be in the state of motion of rest untill and unless an external force is acting on it. To prove or verify it experimentally today, is there any way ...
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1answer
40 views

What force counteracts friction when a block is pulled?

Firstly, I understand and apologize that this is more of a physics question than a math question. I noticed that when I pulled a book out from under a pack of gum, the gum stayed largely in place (it ...
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3answers
1k views

The physical definition of work seems paradoxical

So this is possibly a misunderstanding of the meaning of work, but all the Physics texts, sites, and wiki that I've read don't clear this up for me: In the simplest case with the simplest statement, ...
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1answer
43 views

Torque due to Gravity

I have learned that a torque on an object due to the gravity can be calculated as if the gravity acts on the center of mass of the object when the object is near the surface of the earth. Now I want ...
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0answers
37 views

Inclined conveyor belt mystery

The situation An inclined conveyor belt with topmost point $h$ height above the ground receives sand at a constant rate $X$ from a container at a negligible height above the lowermost point of the ...
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3answers
919 views

What determines whether a pool ball will bouce backwards after colliding with another pool ball?

I'm no knowledgeable pool player, but I've noticed that sometimes when the cue ball hits another pool ball, they roll together; and sometimes the cue ball bounces back. And I have a very, very rough ...
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0answers
45 views

How to find the force to cause certain trajectory? [closed]

So I got a little board today and decided to do some physics. What I came up with is confusing me alot. Say someone throws a rock and when this happens you get the known's of. From here is there a way ...
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1answer
39 views

Physics of Snow Globe

What is the physics behind snow flakes inside a 3D snow globe? If I were to implement a snow globe in computer graphics what kind of model do I need to the flakes motion like a real snow globe? What ...
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2answers
38 views

How would an earth-spanning ring around the equator behave?

If a ring/belt would be constructed of a sufficiently strong material around the entire equator at 100m height from the surface assuming the land/water beneath is flat (no mountains get in the way), ...
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4answers
150 views

How to calculate a collision which is partly elastic and partly inelastic?

(For the purpose of this question, "calculating a collision" means: given the velocities and masses of two objects in a collision, figuring out the new velocities of both objects after the collision). ...
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1answer
54 views

How to calculate energy to start movement?

So let me try to explain a little bit. Lets say I have a robot on wheels. I want this robot to push a block. Lets say the force to produce in order to move that block is 100N. How much energy will I ...
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2answers
63 views

Add weight in front or behind the moving wheel?

Consider a wheel with bearing and axle bar rolling on level ground. If I want to help the wheel continue moving longer(or faster speed), should I add weight by moving the rider body in front or ...
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1answer
42 views

Force to stop a moving rope vs. stagnation pressure of a fluid

Let $\lambda$ be a linear density of a rope which is moving into a scale at velocity v. The additional force on the scale due to the collision is given as $\frac{d p}{d t} = v\frac{d m}{d t} = ...
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1answer
33 views

What will be the acceleration of an object $A$ when its released by another object $B$ moving with an upward acceleration $a$?

What will be the acceleration of an object $A$ when its released by another object $B$ moving with an upward acceleration $a$? Will the acceleration of the object $A$ be more than the acceleration due ...
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1answer
60 views

Why does Newton's Third Law not preclude any motion at all? [duplicate]

When walking, if I apply a force of 2N on the earth, the earth applies a force of 2N back on my feet due to Newtons 3rd Law of Motion. These 2 forces are equal in magnitude but opposite in direction, ...
2
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1answer
51 views

Magnetic field and Newton's third law

If a magnet exerts force on a iron block (opposite and EQUAL), does a iron block also exerts force on magnet (via Newton's third law)? If yes then what magnetic property does it has to produce equal ...
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1answer
54 views

Existence and Quantum Mechanics [closed]

I am not a physics major but I'm interested in studying quantum mechanics. Does matter (or energy, they're the same anyways :P) really gets created and destroyed very fast in a subatomic field or in ...
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0answers
31 views

Blocks crushing blocks [closed]

A building has 100 floors. Each floor is 3 metres high. Each floor can support 3 times the weight of those above. Floors 82 and 83 are removed instantaneously allowing the 17 floors above to fall 6 ...
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1answer
58 views

Dropping a ball in a fast moving train

If I drop a ball in a train moving at a constant speed, will it land on the spot I aimed it at or a little away as the train has moved while it was in air? If it lands away, will the observer not know ...
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2answers
70 views

Electrical force between two objects

I tried to solve the following problem: There are 2 objects . The object m1 with charge q and the object m2 with charge q.(same charge).The object m2 is connected with a rope to the ceiling. at the ...
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0answers
18 views

Does a pivot exert an additional force, normal to the centripetal force, on an object rotating about it?

A thin plank of mass $M$ and length $l$ is pivoted at one end. The plank is released at 60$^{\circ}$ from the vertical. What is the magnitude and direction of the force on the pivot when the plank ...
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3answers
697 views

Ball thrown from a moving train

This is not a question about throwing a ball vertically in a moving train. I am asking what would happen if I throw a ball in a horizontally in a moving train. Assume I am facing an exit door of a ...
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0answers
40 views

Does a rotating plank only acquire rotational kinetic energy?

I have another doubt with a Kleppner problem :(. A thin plank of mass M and length l is pivoted at one end. The plank is released at 60$^{\circ}$ from the vertical. What is the magnitude and ...
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1answer
46 views

Does a spinning part affect the moment of inertia of a composite object?

I have been going back through some Kleppner problems and have a doubt concerning problem 6.18. It states: Find the period of a pendulum consisting of a disk of mass $M$ and radius $R$ fixed to ...
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1answer
33 views

Relative wind velocity explanation - understanding Irodov problem 1.6

I am having trouble understanding the reasoning behind the solution in this Irodov General Physics problem. The problem is 1.6: 1.6. A ship moves along the equator to the east with velocity vo = ...
6
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5answers
228 views

Acceleration in $F=ma$

I tried to ask this question in Electrical Engineering Stackexchange but was told I was better asking here. Newton's Second Law of Motion states that the vector sum of the forces $\mathbf{F}$ on an ...
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5answers
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Why are these periods the same: a low earth orbit and oscillations through the center of the earth?

Related: Why does earth have a minimum orbital period? I was learning about GPS satellite orbits and came across that Low Earth Orbits (LEO) have a period of about 88 minutes at an altitude of 160 ...
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0answers
19 views

How is work done by a system in static equilibrium? [duplicate]

For a little colour: this came from my wondering why fork-lifts are hydraulically driven, rather than electromechanically. My question is this: why is it that some systems, while in static ...
0
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1answer
32 views

Apparent weight on a hill and in a ditch [closed]

first time posting. I'm trying to solve these 2 problems. I have a solutions I just don't know if I'm right...seems odd that they are the same answer... 1) If you are driving over a hill of ...
2
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0answers
49 views

How to calculate launch angle for tangentially launched satellites?

What is the value of theta for a satellite not falling back to the Earth if it is launched from the direction tangent to the surface of the Earth? I have found the escape velocity which is 11.18km/s, ...
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0answers
30 views

How can we describe the trajectory of an object projected into a viscous fluid?

Can we quantitatively describe the motion of a particle inside a fluid? Let us consider the case when an object (say a sphere, so that stoke's law holds true) is projected into a fluid of viscosity ...
1
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4answers
100 views

Is it possible to prove that projectiles with drag will not travel in a parabola under the theory of classical mechanics?

Can you prove that projectiles will travel in a parabola, provided the acceleration due to gravity $g$ does not vary significantly along the trajectory? This should take air resistance into account. I ...
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1answer
24 views

How to calculate required energy to displace a pendulum?

How can one calculate the amount of energy needed to displace pendulum with given mass m and string length L to $\alpha$ degrees from resting position when acceleration due to gravity is known?
3
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2answers
120 views

What is the mathematical definition of work?

I'm looking for the pure mathematical definition of work, but I haven't yet learned line integrals. My book says that the work due to a force ${\bf F}$ from point $A$ to point $B$ is $$ W= |AB|\cdot ...
6
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2answers
93 views

When falling through the air, does swinging arms/legs actually help anything?

Let's say someone jumps off an Olympic-sized diving board into a pool below (so air resistance is negligible). As soon as they jump, they start swinging their arms. Does this help them stay upright ...
0
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1answer
34 views

Calculate the weight that a hot air balloon can carry [closed]

Given a hot air balloon of radius 10 meters and negligible mass, calculate the maximum weight it can carry if the density of outside air is 1.2 $\frac{kg}{m^3}$ and the density of inside air is 0.9 ...
3
votes
2answers
170 views

Potential energy of a rotating bar

I have a bar of length $L$, mass $m$, and negligible width. The bar can rotate along an axis through its center of mass (the rotation is in the $x$-$y$ plane), and also can move up and down (in the ...
3
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2answers
107 views

Physical Role of Batter in Baseball

Physically, what is the role of a batter in baseball? My question is inspired by How does the speed of an incoming pitch affect the speed of a baseball after it's hit? The answer to that question, ...
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0answers
15 views

Is acceleration quadratic or linear outside of a gravity field? [duplicate]

So as I understand it: If you hit a wall at twice the speed you hit four times as hard? I often ask people this and everyone says "at twice the speed you hit twice as hard". $K=\frac{1}{2}mv^2$ is ...
2
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1answer
41 views

Period of pendulum in falling lift

A simple pendulum suspended from the ceiling of a stationary lift has period $T_0$. When the lift descends at steady speed, the period is $T_1$. When the lift descends with constant downward ...
6
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1answer
348 views

How does my kitchen scale know I'm holding it?

If I switch on my electronic kitchen scale while it's on the table, it reads 0 grams. If I pick it up, it reads around -500 grams. Conversely if I switch it on in my hand it tares to 0g and then reads ...
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1answer
57 views

What force does a tall building exert on air?

I once heard that a tall building, let's say 10 stories, actually causes wind to blow by virtue of simply existing. It also was said that is why metropolitan downtown areas tend to be windy. What are ...
1
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2answers
106 views

Kinematics question - Newton's Law of Motion [closed]

Question: Find the mass M of the hanging block in the following figure which will prevent the smaller block from slipping over the triangular block. All the surfaces are frictionless and the strings ...
0
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1answer
29 views

Kinematics - moving body [duplicate]

If I have an inclined plane, which has acceleration $\alpha$, will a block placed on the inclined plane slip back with the same acceleration? (considering that the surface is frictionless)