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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Do we need Escape Velocity

This may seem silly a lot but I really need some clarification on the necessity of escape velocity for a rocket leaving the Earth's gravity. A stone thrown vertically upwards reaches to a certain ...
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3answers
39 views

Intuition behind Rocket propulsion equation [on hold]

What's the intuition behind the Tsiolkovsky rocket equation: $$v - v_0 = v_{ex} \ln{\frac{m_o}{m}}.$$
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1answer
24 views

Potential Energy, Kinetic Energy, velocity, question?

A man standing a certain height above the ground throws a rock straight up with an initial velocity of $10 \:\mathrm{m/s}$. A few moments later, the rock hits the ground with a kinetic energy of ...
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2answers
37 views

What is the minimum velocity a toy car has to travel in order to survive going through a loop of radius 0.2 meters?

I tried height = 2 * radius = 2 * .2 m = .4 m. Potential energy = mgh. Kinetic Energy = $\frac{1}{2}mv^2 = mgh$ Then $\frac{1}{2}v^2 = gh$ $v = \sqrt(2gh) = 2.8 m/s$ The correct answer is 2 ...
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2answers
46 views

Is my answer possible? (Newtonian Third Law Pairs and Forces, Multiple Choice Word Problem)

So I recently took a test and the teacher graded my answer correct, yet my friends saw that the other answer was correct and they protest that it should be the right answer: The question goes: ...
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0answers
20 views

equilibrium pulley system [duplicate]

the question asks what mass i need for m1 to be in static equilibrium while m2 is given as 60kg. im not sure first of all if that means the two masses have to be equal in length balanced. secondly, ...
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1answer
51 views

How do I find the angle given the mass, the acceleration and the force acted on a body?

My Issue I have the mass, the horizontal acceleration and a force that acts on a body. The force forms an angle $\alpha$ of unknown degrees with the x-axis. I would like to know how I can find the ...
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0answers
55 views

mass needed for equilibrium in pulley system [on hold]

Question says: For what m1 will the illustrated pulley system be in static equilibrium if m2 = 60 kg? ive tried equating the changes in length where change in x1 is equal to twice the change in x2 in ...
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1answer
29 views

Force of impact of a projectile [on hold]

I need to calculate the force of impact of a projectile on a target . The projectile has been fired at an initial velocity $U$ and an angle of departure $X$. The projectile is hitting the target at an ...
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2answers
43 views

How do I find the horizontal acceleration of a body given its mass and the force that acts on it? [on hold]

My Issue I have the mass of a body and the force that is acted on a body. I am trying to calculate the horizontal acceleration and to understand how the horizontal acceleration is connected with the ...
1
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0answers
31 views

Calculation of angular acceleration [on hold]

Hi I am doing a physics question and it's like this: Two identical blocks, each of mass M, are connected by a massless string over a pulley of radius R and rotational inertia I . When the system is ...
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1answer
32 views

I cannot find on the internet, what the roadblock is for this self-replicating robot idea [on hold]

Firstly, you can build a human robot with all the needed solid-state-memory sticks in it to make it build a duplicate human robot with the same amount of memory sticks inside, just that they cannot be ...
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2answers
46 views

Is there a difference between Weight and Force of Gravity?

Is there a difference between Weight and Force of Gravity or they just mean the same thing? My textbook does not clarifies this point. Thank you in advance for your help!
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1answer
30 views

Potential energies of charges and spring

I wonder if someone could sanity check this very simple calculation. Consider a pair of charges $+q$ at rest separated by a spring of length $d$ and stiffness $k$. The spring provides the force that ...
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0answers
22 views

Moment of inertia question 11 [on hold]

A circular disc of radius $R$ and mass $M$ has non uniform surface mass density $ar^2$ where $r$ is the distance from the center of the disc and $a$ is a constant.what is the moment of inertia about ...
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1answer
64 views

How to calculate the energy required to rotate a planet?

How to calculate the energy required to rotate a planet from non-rotating state? Say the planet is Venus with equally distributed mass of $4.8676 \times 10^{24}$ kg, and desired rate of 1 rotation per ...
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0answers
39 views

Is there a typology of different fundamental physical objects?

As I understand it (and of course, I may be wrong!).... In classical mechanics, all objects are basically the same in the sense that They are composed of atoms bunched together. These atoms occupy ...
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5answers
2k views

Zero velocity, zero acceleration?

In one dimension, the acceleration of a particle can be written as: $$a = \frac{dv}{dt} = \frac{dv}{dx} \frac{dx}{dt} = v \frac{dv}{dx}$$ Does this equation imply that if: $$v = 0$$ Then, ...
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2answers
32 views

Confused about the “negative” - “positive” direction in this case [on hold]

If we have a graph on a pc screen of velocity versus time and the line on that graph is pointing downward implying a slope with a negative value which is a.k.a acceleration here. Now, you have a ...
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2answers
58 views

Orbital Velocity Question

I have a satellite in a stable trajectory around Earth, of a Mass $m$. I know that its velocity is: $$ v = \sqrt{mG/r}\, $$ But now it begins accelerating directly against the gravity vector (i.e. ...
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2answers
34 views

Conservation of Momentum: Perfectly Elastic Collision, Example Problem

I am a middle school science teacher. I'm a little rusty on my physics knowledge, and I came across a question that I feel like I should be able to solve, but it also feels like there is a piece of ...
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1answer
27 views

Equations for a collision between two particles

Say I have two particles on a 2D plane, they have a x and y coordinate, a x and y velocity, a mass, a coefficient of restitution and a coefficient of friction. What formulae would I need to determine ...
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0answers
22 views

Launching a Spring from a meter stick [on hold]

In class we are engaging in 'war games'. We receive a random spring and launch it from a meterstick at a target flat on a nearby table. we will have the variables for: ...
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1answer
43 views

Pipe in space outputs gas - what is its angular momentum at $t$ and $t+dt$? [on hold]

Given a pipe in space (neglect gravitational force): The speed of the gas is $v_0$ (in relative to the edge of the pipe) The length of the pipe is $l$ The pipe rests (not moving) at $t=0$ The gas ...
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1answer
29 views

A 45.0 kg girl is standing on a 163 kg plank? [on hold]

The plank, originally at rest, is free to slide on a frozen lake, which is a flat, frictionless surface. The girl begins to walk along the plank at a constant velocity of 1.47 m/s relative to the ...
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2answers
41 views

Does the conservation of linear momentum for a ball hitting a wall and changing direction?

The conservation of linear momentum essentially says: $$\sum m \vec{v_1}=\sum m \vec{v_2}$$ But if I take the absolute value of both sides, and drop summation, is it also equivalent to say that: ...
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2answers
51 views

Would it be possible to make a space elevator only in the atmosphere?

I wonder if with current day technology we could make a "floating platform" which hangs from a satellite by a space elevator. This could allow a "launch process" involving floating a balloon to the ...
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2answers
62 views

Balancing a pencil

I came across this equation for balancing a pencil while solving some problems: $$ml\ddot { \theta } =mg\theta $$ Where $l=$the length of the pencil, and $\theta$ is the angle it makes with vertical. ...
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1answer
26 views

kinematics: parabolic movement [closed]

How does the formula $ax^2$ is affected by the angle and the power of the launch of, let's say, a cannon ball, (regardless of its mass)? I am trying to create a simulation, and everything I have to ...
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2answers
31 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?
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2answers
65 views

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

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 ...
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2answers
21 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 ...
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1answer
20 views

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

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 ...
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4answers
86 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 ...
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0answers
19 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 ...
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3answers
38 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 ...
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1answer
43 views

Can individual forces be regarded as momentum flows? [closed]

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 ...
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0answers
45 views

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

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 ...
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0answers
50 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
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2answers
78 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 ...
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0answers
29 views

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

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
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2answers
36 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
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1answer
45 views

Quantum mechanics for playmen [closed]

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 ...
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2answers
50 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
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5answers
122 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 ...
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1answer
27 views

Derivation for certain non uniformly accelerated movements [closed]

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 ...
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2answers
15 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 ...
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2answers
26 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?
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2answers
74 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 ...
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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 ...