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.

learn more… | top users | synonyms (3)

-1
votes
1answer
12 views

How do we prove that the initial velocity is equal to final velocity relative to centre of mass?

In elastic collision it is stated that the initial velocity relative to centre of mass is equivalent to final velocity of centre of mass of the same object. How do we prove that?
0
votes
2answers
23 views

With what initial speed does the person leave the ground to reach a height of 60 cm?

An average person can reach a maximum height of about 60 cm when jumping straight up from a crouched position. During the jump itself, the person's body from the knees up typically rises a distance of ...
0
votes
1answer
10 views

Can there be friction unless the objects in contact are not acted upon by an external force?

The definition of friction I read from The book, General Physics written by Henry Crew is that, The resistance which either one of the body offers to the motion is called force of friction". If it is ...
0
votes
1answer
18 views

Why Normal force exerted by earth on the body is taken as the pressing force? [on hold]

For a body lying on the earth's surface there must be some laws governing its state. $a_o=0$ $=>$ $\sum F=0$ Since $\sum F=0$ then body is said to be in state of equilibrium. The net force is ...
1
vote
3answers
49 views

How would swimming in low gravity work?

Sorry I know very little of actual physics, I'm not looking for hard and fast numbers just a general idea of how the mechanics would work. For the sake of argument, say you were on a planet or moon ...
1
vote
0answers
15 views

Torsion Spring Moment Calculation

I'm trying to extend the idea of a translational spring to a rotational spring. Consider a spring that acts on all displacements of a body: $$ \mathbf{F} = \begin{bmatrix} F_x \\ F_y \\ F_z ...
1
vote
3answers
28 views

On the definition of elastic restoring force in a spring

How is the elastic restoring force defined exactly for a spring? We know by hooke's law that $$F_{restoring} = -kx$$ but what does $F_{restoring}$ really mean? I thought up till now that it was the ...
0
votes
1answer
39 views

Can individual forces be regarded as momentum flows?

Net force on an object can be defined in two ways equivalently (from a classical point of view): $$\vec{F} = m\frac{d\vec{v}}{dt}=\frac{d\vec{p}}{dt}$$ Looking at the last expression (definition in ...
2
votes
0answers
40 views

How much work can a single grain of rice do? [on hold]

I found a website saying a grain of rice contains 1/10 kcal. I'm not a physicist and haven't done maths for a long time. But here's what I came up with: E = m * g * h One small calorie equals ...
-1
votes
0answers
48 views

Why do motors have a speed limit? [duplicate]

The force which will move a body with this motor will be the difference between the force of the motor say 2N and the resistance - friction force - say 1N then the sum of forces will always be ...
0
votes
2answers
63 views

What does the force mean in $dp/dt$ form?

One was to write Newton's laws is: $$F=\frac{dp}{dt}.$$ I don't understand what is the force there. I believe that $F$ is the net external force on the system. So supposedly I have a mass which is ...
-3
votes
0answers
23 views

Rocket needs to make course correction what mass of gass must be expelled [on hold]

A(n) 5200 kg rocket traveling at 3900 m/s is moving freely through space on a journey to the moon. The ground controllers find that the rocket has drifted off course and that it must change direction ...
1
vote
2answers
29 views

Working out velocity (including air resistance) [duplicate]

For my computing project, I am creating a projectile simulator but I cant seem to get my head round the air resistance. I tried by working out the horizontal and vertical velocity by solving it ...
0
votes
1answer
39 views

Quantum mechanics for playmen [on hold]

I am a student who is working on a small game and I played around with the idea of using Quantum Mechanics as the base of the game. Which concepts and results would be cool to play around with ...
0
votes
2answers
48 views

How does the object at constant speed pass the accelerating object?

A car starts from rest and move with constant acceleration of $4\frac{m}{s^2}$ and at the same time a motorcyclist moving with a constant speed of $36\frac{km}{hr}$ overtakes and passes the car. ...
1
vote
5answers
116 views

Why am I not accelerated by the reaction force applied by Earth on me? [duplicate]

Newton's third law says that "to every action, there is always an equal but opposite reaction". And Newton's second law of motion says that, $F=ma$ $=>$ $a=\frac{F}{m}$. People says that If I stand ...
0
votes
1answer
24 views

Derivation for certain non uniformly accelerated movements [on hold]

A sphere of $m_1$ is thrown at a speed of $v_i$ perpendicular to the surface from the surface into the atmosphere.. Are there equations for position $x(t)$ and the speed $ v(t) $ of the sphere at a ...
0
votes
2answers
14 views

If two bodies move opposite to each other when brought in contact, what is the direction of force of friction?

We know that when a body is at rest and other is dragged over it then a force is produced which opposes the motion and consequently its direction is negative to the force applied on body to produce ...
0
votes
2answers
25 views

If the force of friction is 20 N for a moving body does acceleration increase with the increase of the mass?

A body is moving and the only force acting on it is the force of friction. If we put another body on this moving body somehow the force of friction will increase; does its acceleration change?
1
vote
2answers
58 views

Why is it easier to go uphill on a lower gear?

In cars as well as bicycles, when we are on a lower gear, the driving wheel (the one on the wheels) has a bigger radius compared to when on a higher gear. So on a lower gear the bike/car would move ...
0
votes
0answers
20 views

Dynamic mass or static mass?

I am testing a cantilever beam assuming it as a single degree of freedom system, therefore it can be described by the equation $$m_d \ddot{y}(d) + c_d \dot{y}(d) + k_d y(d) = p(t) $$ Where $d$ is ...
1
vote
2answers
22 views

Understanding incompressibility (of rubber or viscoelastic material)

Literature gives a lot of explanation why rubber is incompressible. However, I still need some thinking to understand physical behavior of rubber or any such material. Often, incompressibility is ...
0
votes
1answer
25 views

How does frequency change with centripetal force?

Using the equation $$F_c = {{mv^2}\over{r}}$$ I can see that mass and velocity are directly proportional to centripetal force. I can also see that the radius length is inversely proportional to ...
30
votes
5answers
4k views

Freefall into snow

In the movie Frozen, the following dialogue takes place: Anna: "It's a hundred-foot drop." Kristoff: "It's two hundred." Anna: "Okay, what if we fall?" Kristoff: "There's 20 feet of ...
0
votes
1answer
37 views

Probability flux: spatial variation of the phase equal to momentum?

We can write any wave function as $$\psi(\vec x, t) = \sqrt{\rho(\vec x,t)}\exp{\left[\frac{iS(\vec x,t)}{\hbar}\right]}$$ for $S$ real and $\rho >0$. Here we interpret $\rho$ as the probability ...
3
votes
3answers
68 views

Velocity increase calculated from kinetic energy in different frames

Say we have an aeroplane cruising along at constant height with velocity $v_0$. It dives by height $h$ and levels out, at a new velocity $v_1$, in a gravitational field of strength $g$. If all the ...
1
vote
3answers
44 views

How to find stopping distance of a car? [on hold]

I am trying to calculate minimum stopping distance of a car once the brakes are applied. I know the velocity at braking instant, i also know the distance from the obstacle. I found out that $$ d = ...
1
vote
2answers
25 views

If I throw a ball horizontally, what are laws, related to Work-Energy concepts, governing that all the situation? [on hold]

In a book, A textbook of physics, There was a statement that when we see a motion of body and start to count the laws related to energy-work concepts governing that motion, we at once find ourselves ...
1
vote
1answer
57 views

Relative acceleration of two planets orbiting a star

Let us suppose we know the radii and periods of two planets' circular orbits around a star -say Earth, Venus and the Sun-, which allows us to calculate the planets' centripetal acceleration, ...
30
votes
4answers
2k views

Intuition as to why the orientation (of a 3D object) is not a conserved quantity?

Say you start off floating in space, in a fixed position and orientation, with zero linear and angular velocity, with no external forces. So you are a closed mechanical system. By twisting your body ...
1
vote
1answer
19 views

Is rolling friction exists only when one body rolls over a plane surface? [on hold]

Suppose We have a circular object (A) and at its centre an circular object (B) of the adjusting size is fitted and then the object (B) (axle) is rotated such that it remains in contact wholly with the ...
2
votes
1answer
40 views

Computing the gravitational force on a planet in a particular system [on hold]

I have a system of four planets moving in a 2D plane. I'm trying to write some code (C++) to find the positions of these planets at time t=3. I'm probably going to attempt this via a leapfrog ...
0
votes
1answer
91 views

Superposition in classical Mechanics

I watched a video in YouTube solved these problem using superposition First he fixed the bottom rope and found the accelearations Second he fixed the upper pulley and found the accelerations Third ...
0
votes
0answers
30 views

Rolling w/o slipping - does a friction force acts in this scenario?

Assume the following scenario of rolling without slipping: A small disk starts rolling w/o slipping at $\vec{r}_{CM}=-9R\hat{x}$ (scenario A) and reaches the bottom of the large hollow disk ...
2
votes
1answer
86 views

If a bullet is fired vertically upwards, when it comes back does it fall to the same spot?

What I'm basically asking is that if a body is projected with sufficiently high velocity so that it doesn't escape from the earth's gravitational field but reaches an appreciable height with respect ...
1
vote
2answers
91 views

Problem with an exercise: position and velocity of a thrown sphere with non uniform acceleration

You stand at the earth's surface, have an object, for example a sphere, of mass $ m_1 $ and throw it with a velocity $ v_1 $ into the atmosphere, perpendicular to the surface. Let $g$ at the surface ...
0
votes
0answers
27 views

problem on electromagnetic induction and newtonian physics

Please imagine a solenoidal toroid (i.e. a donut shaped inductor) powered by an AC voltage source. It creates a changing magnetic field which is confined to the interior of the toroid (i.e. within the ...
1
vote
1answer
57 views

Can two bodies move with equal acceleration if forces acting on both are unequal?

In my textbook there is a case given that is to find acceleration and tension produced in a string passed over a frictionless pulley and attached with bodies of different masses at its ends. Now below ...
0
votes
0answers
24 views

About acceleration in cylindrical coordinates [on hold]

The question is attached as a pic I can't seem to find $\ddot r$ and $\ddot\theta$. Assuming I already got $\dot r$ and $\dot\theta$ (the answers are written after the question). The idea I tried ...
0
votes
1answer
19 views

Conservation of momentum in a superelastic collision [on hold]

http://postimg.org/image/u69jgxn4b/ I am having trouble understanding whether final momentum is conserved in each one of these problems. I have given an attempt in the pictures. I am confident that ...
1
vote
1answer
274 views
0
votes
1answer
44 views

What physics concepts support the observation of the book and paper falling together?

you place a sheet of paper on a book, it falls with it rather than being separated & slowed by air resistance. What physics concepts support the observation of the book and paper falling together? ...
1
vote
1answer
43 views

Is tension in a string is the reactive force produced in a string being pulled at both ends?

In my textbook, the definition of tension was given that Tension is the reactive force which exists when string is being stretched at its both end. After it there was a case given that to calculate ...
2
votes
2answers
195 views

Why are heavy things harder to lift?

According to multiple websites, any object in free-fall (no air resistance) on earth will accelerate towards the Earth at 9.8 m/s. If all objects fall towards the Earth at the same rate, regardless of ...
0
votes
1answer
62 views

How can we prove simply that acceleration for every freely falling body is equal to $g$? [duplicate]

If I allow two bodies of different masses to fall freely from same height towards the earth, how can I prove that the acceleration produced in both was constant and equal to gravity.
-1
votes
0answers
18 views

How can I find the diameter plz [closed]

An industrial mixer accelerates from rest with an angular acceleration of 0.6 rad/s2 to a constant angular velocity in 6 s. If the total acceleration acting on the contents of the mixer must not ...
1
vote
1answer
19 views

Can two bodies of different mass attached at ends of string passed over a frictionless pulley produce equal tension on both sides?

In my textbook there is given a case that to calculate acceleration and tension produced in string when string is attached at it's ends with two bodies of masses such that $m1>m2$ and the tension ...
6
votes
2answers
182 views

Will an object falling into Earth's orbit start spinning?

Assume an object falls towards Earth (I've drawn a hyperbolic orbit, but this would apply to any orbit). The object starts at $A$, and at this point it is not rotating i.e. an observer on the object ...
1
vote
1answer
36 views

Newton's third law of motion versus Work

Newton third law of motion says that "To every action, there is always an equal and opposite reaction". The vector study tells us that if two vectors are of same nature and equal magnitude but ...
0
votes
1answer
38 views

Hooke's Law vs. Elastic Potential Energy

I am currently learning about elastic potential energy and this is a question that was given to us by my teacher: When a 13.2-kg mass is placed on top of a vertical spring, the spring compresses ...