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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3
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3answers
143 views

$F=ma$, so if acceleration is zero the force must also be zero?

I was just pushing a huge rock which I couldn't move at all. Given that the acceleration was zero as a result of my efforts, since $F=ma$, doesn't this mean that the force must also have been zero? ...
2
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2answers
34 views

How can tangential acceleration from a radial force be explained?

A mass is attached to a rope, and put into a circular motion. If I pull the string from the center, the tangential speed of the mass will increase (by conservation of angular momentum). I am ...
7
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3answers
534 views

Can Lagrangian mechanics be justified without referring to Newtonian mechanics?

Are there any ways of justifying Lagrangian mechanics as a foundation of classical physics, without referring to Newtonian mechanics? In other words, what is the deeper reason or intuition why ...
-2
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0answers
11 views

Sliding ladder kinetic energy in generalised coordinates [on hold]

This is a problem from Hand and Finchs' Analytical Mechanics, in a chapter looking at holonomic constraints and generalised coordinates in Lagrangian Mechanics. A ladder of length $L$ and mass $M$ ...
37
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8answers
7k views

Why doesn't a bike/bicycle fall if going with a high speed?

Why does a bike/bicycle fall when its speed is very low or close to zero and is balanced when going with a high speed?
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2answers
211 views

Confused about elasticity and collisions

I was solving the following problem and the explanation to it confused me. There are two objects with mass $m$ and $M$, respectively. The object with mass $m$ has a velocity of $\sqrt{2gl}$ and ...
2
votes
2answers
144 views

Lagrange's equation implying Newton's 2nd law?

The typical first application of Lagrange's equation is showing that it implies Newton's law for a particle whose Lagrangian is $L=\frac{1}{2}mv^2-V(x)$. Plugging this Lagrangian into Lagrange's ...
2
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0answers
30 views

Conservation Laws and Isotropic Time

In most dynamics books I've read they refer to conservation laws and their associated symmetries. I know that the conservation of momentum is a result of the homogenity of space angular momentum is ...
0
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1answer
19 views

What can I say about a graph depicting orbit a particle has gone through? Acceleration VS friction

I have an orbit in which a particle is told to have gone through. There is a straight part, and a curved part. I am asked to mark the right statements, which are: a. Without any further data, there ...
10
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7answers
2k views

Is rotational motion relative to space?

Let's assume that there is nothing in the universe except Earth. If the Earth rotates on its axis as it does, then would we experience the effects of rotational motion like centrifugal force and ...
6
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3answers
356 views

Optimal speed for the water wheel

The hydroelectricity plants extract the potential energy of highly deployed massive object (water) as it falls down. Without turbine, all that energy would be converted into speed (kinetic energy) at ...
0
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2answers
169 views

Ball flying towards me - Newton's third law is violated?

I was trying to answer the question of the flying ball here on the basis of Newtons third law and Momentum conservation. Here is what I have tried. Lets take $m_1$ (the ball) hits $m_2$ (the man). ...
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0answers
45 views

Mechanical energy? [on hold]

A particle of mass $2\,\mathrm{kg}$ is attached to one end of a model spring that is hanging vertically from a fixed point O. The spring has stiffness $4$ and natural length $1\,\mathrm{m}$. ...
2
votes
1answer
84 views

Moving Around Space Without Propellant [on hold]

A mechanism as shown in following picture is floating freely in space. Concentrating on the main components first, which is the long rod in the middle with another 8 smaller rods connected to it, ...
1
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1answer
281 views

Why does the Nusselt Number for a Constant Surface Temperature, Thermally Fully Developed Circular Pipe Converge To a Constant of 3.66?

I have flow in a pipe with a constant surface temperature boundary condition. The velocity profile is fully developed and the temperature profile is also fully developed. In my textbook, it says that ...
7
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9answers
2k views

How to explain independence of momentum and energy conservation in elementary terms?

I'm trying to explain to someone learning elementary physics (16 year old) that linear momentum and energy are conserved independently. I'm not a professional physicist and haven't tried to explain ...
0
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1answer
19 views

What is meant by “method of approximate numerical method” or “method of digital computer” for solving the differential equation of resistive force?

I was reading "motion against resistive forces" in Newtonian Mechanics by A.P. French; here is the excerpt: [...] In general, the resistive force $\mathbf{R}$ is is a function of speed, so that ...
3
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2answers
249 views

Projectile motion maximum distance to origin

Is there an elegant or easy way to derive the maximum distance from the origin to a point of the parabola created by projectile motion (assume initial position is the origin)? Other than ...
0
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0answers
62 views

Centrifugal And Centripetal Forces [on hold]

Imagine a long rod floating in space(negligible gravity). On this long rod are attached 8 other smaller rods with a massive sphere attached to them at the end. They are connected with the long rod ...
-4
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2answers
2k views

If there is no gravity, does that mean there's no mass as well?

I have demonstrated that weight only is measured based on the gravitational pull of where you live. For example, the gravity on the surface of Mars is three times smaller than the gravity on the ...
0
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1answer
39 views

Resultant forces on system of particle is zero , we can have?

This is how the specific question is framed? If the resultant of all the external forces acting on a system of particles is zero, then from an inertial frame, one can surely say that: 1: ...
12
votes
5answers
724 views

Compressibility and the form of Newton's second law in fluid mechanics

In deriving Euler's equations for fluid mechanics, in particular $$f=\rho \partial_t v +\rho v\cdot \nabla v$$ for some body force $f$ (e.g Landau & Lifschitz 2.3) one assumes the continuity ...
0
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1answer
40 views

Maximum range of projectile from elevation, simply?

Let us say you have project a ball at velocity $u$ from a cliff hight $h$, and we want to find the maximum range of the ball. Ok so you could do this using equations of motion (for constant ...
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2answers
581 views

Is my understanding of the mechanics of skidding correct?

I'm trying to understand the mechanics which determine if a car making a turn will skid. Are the following correct or incorrect: A vehicle making a turn will skid unless the centripetal force is ...
3
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4answers
1k views

Can internal forces do work?

My Mechanics textbook claims that the sum of the work by internal forces is not generally zero. translated to English the paragraph reads: Notice about the work by internal forces: the work by ...
2
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1answer
79 views

Understanding Millikan's oil-drop experiment

This is quoted from A.P. French's Newtonian Mechanicsabout Millikan's oil-drop experiment: The droplets randomly produced in a mist of oil vapor are of various sizes. The ones that Millikan found ...
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0answers
29 views

How does the elasticity of a ball influence its behaviour during collision?

The problem I am trying to solve is as follows: A football made of rubber with mass $m$ rolls on a table at speed $v$ and angular speed $\omega$ until it hits a player. Some sort of deformation ...
0
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0answers
11 views

How to calculate the steps needed for a motor to rotate a circular object in a pulley configuration? [on hold]

I have a stepper motor with 200 steps per revolution and a pulleys configuration as following: 3 pulleys with 100 mm diameter each on 1184 mm PCD and are equally spaced (120 degrees) from each other. ...
0
votes
1answer
91 views

Derive Equation For a Cantilever in SHM

I am currently investigating how a hacksaw blade's time period of oscillation changes when I add mass to the end of it or when I change the length it is clamped at. I found the following equation ...
1
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1answer
30 views

How is the kinetic energy of the wind transferred onto a lift based wind turbine?

The rotor blades of a lift based wind turbine are shaped like airfoils, so the wind flowing around them creates a lift force which in turn moves them around. From a thermodynamic viewpoint and like ...
-3
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0answers
30 views

Hooke's law question of physics [on hold]

A spring has a length of 9cm when loaded with a 200g mass. The 200g mass is replaced with a 100g mass. What is the new length of the spring?
0
votes
1answer
59 views

Which point in the graph does a parachute open?

The diagram represents speed-time for a sky diver. He falls freely from an aircraft then opens a parachute and later lands safely on the ground. At which point did the parachute fully open? ...
3
votes
1answer
173 views

Approximations in simple pendulum

In the approximation $$-(g/ \ell) \sin \theta \approx -(g/ \ell) \theta $$ we make an error $R$ which is $O(\theta ^3)$. If i did well my calculations it is estimated by $$R\leq|(g / ...
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2answers
104 views

Finding sphere of influence in multibody system

I would like to draw a boundary illustrating the sphere of influence of each body in a 3 body system. What is the best way to find such a boundary? My understanding is at the edge an SoI is the ...
2
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2answers
76 views

A car with constant speed doing a turn

Let's say we have a car with four wheels and the center of the car has a speed of 50km/h. There is no friction or air resistance. If the car is moving straight each wheel will also have a speed of ...
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0answers
13 views

What motor is required to run lift 200 kg on 25 feet? [closed]

I am working on a Lift project for a wheel-chair , & i am wondering what power of motor and pulley is required for 200 kg , 1 person lift.
-1
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0answers
18 views

Find how much does the spring extend [closed]

A mass m body is attached to the spring and rests on the board so the spring is not stretched. The board starts to move with an acceleration a. How much does the spring stretch at the moment when the ...
0
votes
1answer
46 views

Time to fall in a non-uniform gravitational field

In an uniform gravitational field the loss in potential energy (the work) done by gravity is given by $\text{-}mg\Delta h$ and the time to do so (assuming no friction and no initial velocity) is given ...
2
votes
2answers
298 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 ...
2
votes
4answers
357 views

What causes a car's velocity to follow the front wheels' direction?

I'm trying to simulate a car with correct physics models. In this example we let the car have a constant speed, and there are no forces (friction and drag) to slow down the speed. Here's a video that ...
-6
votes
0answers
42 views

physics question.. please help! [closed]

A 68-kg woman stands on frictionless level ice with a 0.8-kg stone at her feet. She kicks the stone with her foot so that she acquires a velocity of 2.7 cm/s in the forward direction. The speed ...
0
votes
1answer
26 views

Pendulum clock delay of time everyday caused by Earth's rotation [closed]

I need to solve this problem: A pendulum clock which gives the correct time at a certain place on the Earth's ground is taken 320 meters high (from the ground) to a tower's very top. Q: How much ...
0
votes
3answers
149 views

A Falling Chain

A chain hanging from a string just touches the surface of the weighing machine. The string is burnt, and the chain falls on the weighing machine. What would be the weight registered on the weighing ...
3
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2answers
56 views

Force amplification and Newton's third law

Pascal's principle in hydraulics leads to force amplification which is a common feature in hydraulic brakes and hydraulic press. A small force applied on a piston of small cross sectional area ...
0
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1answer
67 views

Do we all actually just weigh half of what our bathroom scales tell us?

Here's the reasoning: Newton's third law tells us that every force has an equal but opposite reaction force. So besides my weight pushing down on the scale from above, there's also an equal force ...
2
votes
0answers
86 views

Minimum energy required to roll a cuboid through $90^\circ$ [closed]

I'm stuck on this textbook question about the minimum energy required to roll a cuboid through $90^\circ$ from an upright position to a horizontal position (see image). I believe the correct answer is ...
2
votes
2answers
378 views

Why ballasted gliders fly faster

The fact: Gliders have ballast tanks that can be filled with water. The addition of ballast increases weight, and this allows the glider to fly at faster airspeeds while maintaining the same glide ...
4
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3answers
74 views

Ball on a slope with hollow

The experiment shown in the image suggests that ball B will reach the goal faster than ball A although the balls have identical properties and they start from the same height. The authors even ...
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0answers
32 views

What is the velocity of a ball on a quarter-circle ramp (with friction)? [closed]

A block of mass m is positioned at the top of a quarter-circle ramp with radius R and friction coefficient μ I would like to find the velocity of the block as a function of μ, R and θ So far I ...
2
votes
3answers
267 views

Power to suspend a mass in air

How much power is needed to suspend a mass in the air? The four parts below deal with the same problem. I post them all here, should there be some subtle things I didn't see. The textbook problem A ...