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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Calculate acceleration based on differential pressures

In my example, water is in a tube and is being accelerated by a compressed air. I already know that $P = \frac{F}{A}$ so if you know the pressure and you know the surface area its acting on, you can ...
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0answers
23 views

How to describe the forces on a weblock?

I am trying to figure out the forces on a weblock when two strands of webbing are wound around it. I have made an attempt but would like to know if I am on the right track or not. A short background, ...
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1answer
35 views

Motion under gravitational forces

In a system of particles, can a particle be considered to be attracted to the combined center of mass of the other particles if the Newton's universal law of gravitation is used (the inverse square ...
2
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3answers
133 views

Where does the energy go when engine braking?

If you're in gear in a car and not accelerating, the car slows down faster than it would from just air resistance and tire deformation. In normal braking, the energy is turned into heat from the brake ...
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2answers
129 views

Is the work done by friction on an accelerating car zero?

Consider a car is accelerating and its tires are not slipping ,just rolling.what is the force on the car that changes its kinetic energy? Some people say in the definition of work dw=F.dx that dx is ...
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2answers
73 views

Total Momentum in the Center of Mass Reference Frame

For solving problems involving elastic collisions it is useful to use the center of mass reference frame as to avoid quadratic equations. However, I am confused about why the total momentum in the ...
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2answers
55 views

Blocks spring system

Two blocks of masses $m_1$ and $m_2$ are connected by a mass less spring of constant $k$. The blocks rest on a rough floor with the spring in its equilibrium length. Coefficient of friction between ...
2
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4answers
70 views

Why do heavier objects provide more reaction force?

According to Newton's third law, to each action there is an equal and opposite reaction, which means that no matter how heavy is the object, if I give it X amount of force, it will give that force ...
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0answers
23 views

Centre of gravity: Adjusting position

If an object is freely suspended from a pivot, why does the centre of gravity fall directly below that pivot? Would this be the same in non-uniform gravitational fields?
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1answer
36 views

Water coming out of a vertical tube lifts a weight to a certain height [closed]

Before I even start the question I would like to apologize in advance for some grammar mistakes since I translated this question from another language. Water is coming out of a vertical tube at a ...
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1answer
61 views

Homework Question: Moments [closed]

Can someone please explain this question? My work: If we take B to be the pivot then as B gets closer to mg the torque due to mg gets smaller, but I don't really see how this affects the force F (I ...
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0answers
22 views

Mechanics & mechanical engineering [closed]

If an object free fall to Earth from very far distance much larger than Earth radius, time taken to complete first 1/2 of journey is approximately 9/11 of time spent for whole journey. How to prove ...
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3answers
52 views

Is this thought regarding work and potential energy correct?

I am really confused about this. The potential energy acquired by an object is equal to $mgh$, if we are on any planet, where $g$ is the planet's gravitational acceleration, which directly comes from ...
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1answer
37 views

While jumping in a high speed train why we fall on same place? [duplicate]

while we jump inside a high speed train why do we fall on the exact place? as train is in high speed and we are jumping so we should fall backside. but this doesn't happen why?
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0answers
29 views

Simple harmonic motion in a horizontally accelerating lift [duplicate]

How would the time period of a pendulum in a lift be if the lift was accelerating horizontally to the right ? My teacher did it by putting a pseudo force "ma" to the left, then getting the resultant ...
1
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1answer
48 views

Force felt by parachutist when opening the parachute [closed]

When falling down with air resistance, y-axis vertical (positive is up), x-axis is horizontal, we have that: $F_y=-mg-kv=ma_y$, where $k$ is the drag coefficient. Now if the man opens the parachute, ...
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1answer
48 views

Hot air balloon trajectory predictions

Hey there Physics friends! I've been struggling with what seems to be a very basic physics question. Let's say that I have wind vector for a given altitude and location, and I want to calculate the ...
3
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1answer
84 views

What is the probability of two bullets to get clashed? [closed]

I was surfing on Instagram, and I found this amazing proto whose description is "the probability of such an event to happen is incredibly small, so this is a really curious finding". Well.. I'm ...
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5answers
93 views

How can escape velocity and gravitational potential be higher in weaker gravitational fields?

on Earth we have an escape velocity of about 11180 m/s and a gravitational field of g=9.81 m/s^2. It would seem obvious that the escape velocity was higher for stronger gravitational fields. Often it ...
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1answer
41 views

Free fall vs throw with air resistance

If I let a stone drop from a certain height and throw a stone from a certain height, with air resistance, which will reach the ground first? When I draw a free body diagram the air resistance in the ...
3
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3answers
77 views

Could the Earth-Moon rotation period equal one Earth year?

I just stumbled on this rather confused QA. The point seems to be if the Earth-Moon rotation period was identical to the Earth-year, then ... ... all three would stay in a line at all times. ...
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0answers
50 views

Free body diagram of pulley

Is there any difference between the free body diagram of fixed pulley and movable pulley? I've read that both of the rope of fixed pulley and movable pulley have the same direction (both upwards or ...
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1answer
66 views

How does Newton's third law work

This law states that to each action there is an opposite and equal reaction. and I understand that this is the law that Rocket thrusters are built on. they use the combustion of fuel to push out hot ...
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1answer
56 views

Basic physics question from a starting physics student [duplicate]

When regarding Newton's 3rd law, I have a question. It seems like while I study, there is no reaction, the actions act at the same time. Is this correct? And also, I really don't understand why ...
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1answer
41 views

Why does the mechanical advantage of a wedge use the length along the slope?

Since mechanical advantage is concerned with force, shouldn't the mechanical advantage of a wedge be calculated using the length of the wedge that's parallel to the applied force rather than the ...
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1answer
36 views

Concept of Work & Energy with trolley Example

I was solving one question in which girl on trolley of certain masses sits. Then certain force is applied on trolley which made some displacement. In my opinion work should be done by both Girl & ...
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1answer
60 views

when does Newton's third law of motion come into effect

I'm a bit confused about when does Newton's third law come into effect and when it does not. For instance, lets say i was swinging a YoYo in a vertical circular motion, I would obviously have to ...
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1answer
93 views

Distance from Earth where gravity becomes negligible

This is a basic little problem I thought up when trying to remember some physics, and I wanted to see if it's at all correct: trying to figure out the distance from earth where gravity becomes ...
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2answers
82 views

Tension of a string rotating a ball in a circular motion?

A ball of mass 5kg is attached to a string of length 120 cm and rotating vertically at a speed of 10 cm/s. what is the tension of the string when the ball is farthest to the right from the ...
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1answer
37 views

Clarification on what inertia and area moments?

This is something I have never understood despite applying the formulas in many classes. What I'm hoping to find here is some clarification. My understanding is that the first moment of inertia is ...
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1answer
73 views

Can you answer these two difficult vector questions? [closed]

Figure 1 1) Determine the value of FB. 2) Determine the magnitude of FA + FB. (I know that the answer must be in Newtons. But other than that, I've very lost on what to do next. Please help!)
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1answer
118 views

Maximum period of a vertically spinning ball [closed]

Problem: A point mass with mass $m$, tethered by a string of length $R$, is in unforced circular motion in a gravitational field with strength $g$. The plane of motion is parallel to the ...
0
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1answer
84 views

Quadratic drag projectile motion

I have calculated formulas with 1 dimensional trajectory motion (free-fall) including quadratic drag, and have created the following equations. These equations of motion are not of much use on its ...
-3
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2answers
86 views

Are Newton's Axioms really axioms? [closed]

What is the absolute Logical origin of Newtons three axioms? Have physicists worked out what is the fundamental reason for actio = reactio and other things?
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2answers
56 views

Does towing a car make moving it easier?

once i saw a diagram in some of my books , of a car being towed by a big vehicle that was sort of a truck. now today that i am studying work , that picture somehow popped in my mind. it looked mostly ...
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6answers
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How does a spinning object “know” that it is spinning?

I am constructing a thought experiment about a spinning object that is floating in intergalactic space. I assume that this object is about the size of a planet so that it will have enough gravity so ...
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0answers
16 views

How does the football curve after the direct free kick? [duplicate]

You might have seen that in football, if a player is awarded a Direct Free kick just outside the penalty box and he kicks it, sometimes the ball does not go in a straight line rather it curves in the ...
0
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1answer
36 views

Rolling cylinder on frictionless inclined plane

A cylinder is kept on frictionless inclined plane. Why it does not roll (it slides only), although torque with respect to contact point is working on it (due to component of weight parallel to ...
4
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2answers
41 views

Finding the Force of two objects - by using Acceleration but only ONE of the given masses?

I came across the following question in my physics textbook and wanted to try to solve it: A 1700 kg car is towing a larger vehicle with mass 2400 kg. The two vehicles accelerate uniformly from a ...
3
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2answers
51 views

Where is the space elevator falling? And the cable holding it?

I guess the concept of a space elevator is pretty well known. The idea, first published by Konstantin Tsiolkovsky in 1895, and popularized (among others) by Arthur C. Clarke in The Fountains of ...
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2answers
82 views

Is there such thing as a critical value for the coefficient of friction?

Is it possible for coefficient of friction to be so high that no matter what force is applied to an object, the object will never move? For example, if I have an incline and a box on the incline ...
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2answers
95 views

Is surface tension characteristic of a fluid?

Does surface tension depend only upon the nature of the fluid or on other factors too like the liquid-solid or liquid-gas interface? I saw in my book definition that $$S = U/A,$$ where $U$ is the ...
0
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1answer
44 views

Change of energy into friction?

If I am pushing a car and it does not move, I am doing no mechanical work. However, I am changing the energy that was stored in my cells into heat energy (maybe sound energy if my hand slips off the ...
1
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1answer
56 views

Conventions and realities of kinetic energy?

I am having doubts regarding why $1/2$ is present in kinetic energy and if this is conventional why cant we say potential energy is $2mgh$ and kinetic energy $mv^2$. So is this $1/2$ conventional or ...
0
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1answer
43 views

Forces in a body falling with air resistance

I would like to know why when a body falls with air resistance, we have that the drag caused by the air is -kv and the acceleration is -mg. What I don't understand is how they both have the same sign ...
1
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3answers
143 views

Free Fall with Air Resistance

Can somebody help me understanding why when free falling the force on the vertical axis is F= -mg-kv, where k is the constant of air resistance and v the velocity? Suppose the vertical axis is ...
1
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1answer
54 views

Parachute jumping with air resistance

I need to write down a model for a man parachuting from a plane at a height h above the ground, having a velocity Vplane. I've had a look at many models online and they all start saying that ...
-1
votes
1answer
21 views

Are cumulus clouds analogous to airships flying downwards?

First of all, cumulus clouds are amazing. Big puffy white clouds floating on the air. Some of them produce updrafts of over 100 Km per hour. Now, if an airship had its engine pointed towards the ...
0
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3answers
77 views

Why is work a scalar quantity?

If the displacement is in the direction of the force, then work is positive. If the displacement is in the opposite direction of the force, then work is negative. If the displacement is perpendicular ...
0
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2answers
66 views

The relation between acceleration and inertial force

Acceleration causes inertial force, and it is not relative, but why? What is the reason for feeling inertial force by acceleration?