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Questions tagged [newtonian-mechanics]

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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Interesting “paradox” from class: Impulse on a rod in a vacuum results in different energy in dependence on point of impulse

This question has been somewhat addressed here, but the discussion ended a little too soon in my opinion. (Sadly, I cannot simply comment in the thread due to low reputation). Say we have a rigid rod ...
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Exact equation of exponential curves of underdamped harmonic motion

I was studying the underdamped harmonic motion and got curious about the fact that the decreasing exponentials $\pm Ae^{-\gamma t}$ are good approximations only for light damping $(\gamma<<\...
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Energy of an object

When an object goes up we say that it gained potential energy but it is doing positive work on the earth so it should lose energy.Please tell correct me.
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Why are tail rotors in helicopters vertical?

I guess spinning in perpendicular direction to main rotor is better in counteracting the torque but what's the mechanism at work?
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Clarification on Soloman A-Level (M1) moments question

In this M1 Soloman paper in Q3(b), we are asked to find in the form $k\sqrt{2}$ the value of force $X$ given that the resultant moment of all forces about $D$ is zero in the following square of width/ ...
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To find the linear acceleration,angular velocity and friction acting on a object which can roll [on hold]

Consider a Sphere,cylinder or any other object which can role.It is on a surface of coefficient of friction μ.A force of magnitude F is applied at an angle θ to the horizontal at the bottom of the ...
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1answer
21 views

Inclined plane vector

I have a question, I need to find $P$ in the following situation. A box of mass 5kg is in equilibrium on a slope at $pi/6$ from the horizontal. I need to find the magnitude of the force in the ...
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1answer
31 views

Noob question about centripetal acceleration

This is a very simple question, but one that has been bugging me since long. Consider a rod of length $L$ and mass $m$ to be hinged at one end. It is vertical initially. It is displaced slightly from ...
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What's the most efficient way to walk and swim?

I hope this is the correct forum for this question. I have two related questions that deal with the same issue. My primary question is regarding swimming. I've found that extending my stroke (...
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To find that curve for rolling ball [on hold]

For a given distance $D$ to be covered by a ball of a given radius $R$, what should be the trajectory of path (in 2D and in 3D) so that the ball (without any external force acting but only) under the ...
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1answer
34 views

Hooke's Law and Overstretched Springs

Recently been working with Hooke's Law at university. My experience of real springs tells me that stretching to a certain point causes the spring to lose "springiness". (Not sure if "elasticity" is ...
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1answer
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To find the acceleration of three blocks and the tension of strings if they are horizontally placed and pulled from the Right side [on hold]

Find the Acceleration of blocks A, B and C, and tensions in the strings. All the blocks are of equal masses of 10kg. Also F = 60N. Let's name the leftmost block as A, middle one as B and Rightmost ...
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Action reaction pair rapidity or time delay

How much rapid is action reaction force ? Suppose i have a rocket of 10kg dry mass and 10kg reactive mass. On launching, 5 kg of reactive mass is burnt. And i get a thrust of 200 N. What will be the ...
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1answer
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Pressure on side walls of container [duplicate]

My textbook mentions the standard derivation of finding pressure at a depth of a liquid by considering a cylindrical portion of liquid an then using the equilibrium of forces and hence pressure comes ...
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0answers
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The minimum force required to move the block is [on hold]

My question : A block of mass 4 kg is placed to a rough vertical wall with a normal force of 100N.The coefficient of static and kinetic friction are 0.5 and 0.3 respectively. The minimum force ...
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1answer
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Reversibility in newtonian mechanics

It will be slightly different from related questions. When we write newton's differential equation $$\ddot{x}=\frac{d^2x}{dt^2}=m\,a$$ we see that reversing time doesn't change the force, but it ...
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What is the deep “physical” intiutive meaning of torque? [duplicate]

There is a rule that $$lever\;arm(1)\times force(1)=lever\;arm(2)\times force (2)$$ This is because the torque equivalence principle. I am only talking about vertical forces (so cross products' mods ...
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Newtons second law appliance [on hold]

Assume we have one box, and we put another box on it. A box of $m_1=4\ \rm{kg}$ and a box of $m_2=2\ \rm{kg}$. The box with more mass ($m_1$) is in the bottom. What will happen if we apply a force of ...
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2answers
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Is time/gravity the source of all energy? [on hold]

I have always been confused about the concept of potential energy. If you raise an object $X$ meters above the ground, it gains $Y$ energy. Simple enough, however, what happens when you keep moving ...
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1answer
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Proof of the Law of the Lever

Is there an accepted proof of the Law of the Lever? I know of several attempted proofs, such as Archimedes's, but these either are incomplete or do not transfer to the setting of Newton's Laws. (It ...
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Newton's Third Law bulldozer and pulley system [on hold]

A 3.74×104 kg bulldozer pushes a 9.35×103 kg boulder. If the wheels of the bulldozer push against the ground with 66800 N of force, what is the magnitude of the force between the boulder and the ...
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Angular momentum with magnetic field

I was computing the Lagrangian of an electron in the presence of a constant and uniaxial magnetic field. Indeed it comes out that, $$ p_r = m \dot{r} $$ $$ p_\theta = m r(\dot{\theta}-\omega_c/2)$$ ...
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Why does a gyroscope increases its velocity when it has a frictional force related to it? [on hold]

When a gyroscope is precessing in a certain angle different than the parallel with the weight of the gyroscope, the velocity of the body increases. Why does it happen?
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How to calculate torque for a linear slide pulley?

I have a linear slide pulley system like in the picture (the string on the right will be attached to a spool, which is attached to a motor) and I'm trying to determine the right motor to buy to power ...
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1answer
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$mg\cos\theta=N$ or $N\cos\theta=mg$ [duplicate]

I was reading up of centripetal motion when I saw the relation that $mg=N\cos\theta$, as can be seen from http://hyperphysics.phy-astr.gsu.edu/hbase/Mechanics/carbank.html, in the case of a ...
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Center of Buoyancy of changing displacement water [on hold]

how do I calculate the center of buoyancy of changing displacement of water?
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1answer
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How does Newton's third law work in springs?

So in high school I thought 'if Newton's third law works, why do springs ever move?' In other words, if I pull on a spring, that means a force of the same magnitude is being exerted in the opposite ...
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Asymptotic behavior of canonical perturbation theory for the classic anharmonic oscillator

What do we know about the asymptotic behavior of the perturbative expansion for the classical anharmonic oscillator? The Hamiltonian is $$ H = \frac{p^2}{2m}+\frac{1}{2}m\omega_0^2 q^2 +\mu q^4 $$ ...
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1answer
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Find the minimum speed of a yo-yo, revolving in a vertical circle, so that the cord does not slacken

A yo-yo is swung with a constant speed in a vertical circle. If the yo-yo has a mass of 80 g and the radius of the circle is 1.5 m, find the minimum speed that this yo-yo must have at the top of the ...
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2answers
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What's the effect of the feet distance on a person's balance in a moving train/bus?

I use metro transit train or bus for commuting to work. I have noticed that when I keep my feet almost shoulder width apart I can easily keep my balance without holding a handle or bars (and even I ...
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2answers
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Question regarding gravitational pull between 2 objects with an object separating them

For illustration sake, envision three objects lined up in a row. The center object would be bigger than the other two. How would the gravities of the masses of the objects on the sides of the bigger ...
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Gimbal camera stabilizer

I want to design a camera stabilizer that stabilizes a GoPro in 3 dimension (pitch, yaw and roll). See the picture for a visualisation. I want to write a simulink model with in it the equations of ...
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2answers
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Work done to change circular orbit and orbital speed

If a satellite of mass $m$ is orbiting a planet of mass $M$ with radius $r_1$ and orbital speed $v_1$ and is brought to orbit at $r_2$ with speed $v_2$, its kinetic energy changes by a quantity $$ \...
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Do Newton's laws imply independence of generalised coordinates and generalised velocity? [duplicate]

When deriving lagrangian formulation from Newton's laws, We use the fact that generalized velocity and generalized coordinates are independent of each other. Is there a mathematically rigorous proof ...
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1answer
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Predicting the effect of a resistive force on a sattelite in orbit around a planet

I'm asked to predict the effect of a resistive force acting on a sattelite of mass $m$ in orbit of radius $r$ around a planet of mass $M$. I have come up with the following equations: Kinetic energy =...
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Elementary physics question related to banking on roads

I am studying 12th grade physics. I encountered this concept while studying circular motion and frictional force. You can find the relevant equations here Friction on roads While practicing the ...
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2answers
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Tension in atwood machine [on hold]

Pretend you have an Atwood machine with a frictionless pulley system. On one end you have a very very heavy mass and on the other end, you have a basically negligible mass such that the combination of ...
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3answers
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Confusion on Independance of Perpendicular Forces [duplicate]

If gravity(vertical force) doesn't affect an object's horizontal motion. So is it saying that weight doesn't affect an object's horizontal motion? And if yes? Why is pushing a heavier object(more ...
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0answers
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Confusion on Independance of Forces [duplicate]

If a perpendicular force is indepedent and unaffected by one another. Why is it harder to move larger/heavier objects, thus slowing the speed of the object. Isn't these two forces (horizontal & ...
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1answer
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Friction & Gravity Relation [duplicate]

Imagine a flat horizontal road surface(made of the same material), the first road is placed on earth, the second one is placed on the moon. 2 cars are placed on both roads and start moving, would the ...
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0answers
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Circular Motion #101 [on hold]

Sarah is playing with her footjump. The ball in her foot jump is in uniform circular motion and makes 20 revolutions in 4s. Find the following: A.) What is its period? B.) What is its frequency? C.) ...
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1answer
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Is friction affected by gravity?

Some people said that moving a car on the moon would make the tires spin a bit more compared to Earth's. But then I started thinking that if static friction and gravity are perpendicular to each other,...
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Calculating time for bodies accelerating together under increasing F_g [on hold]

George Clooney and Sandra Bullock are two astronauts floating in space. They each weigh around $150kg$, including their suits. They're $2m$ apart. JUST out of arms' reach. (I know, it's tragic.) How ...
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1answer
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Angular SHM and center of mass

This has been confusing me for a while. Consider a solid, homogeneous rod of mass $m$ and length $l$, hanging from a fixed pivot. Its center of mass is located at $\frac{1}{2} l$, and its moment of ...
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0answers
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Mechanics and Newton's laws of physics [on hold]

A scissor is used to cut a wire of circular cross section and negligible weight the wire slides in the direction away from the hinge until the angle between the scissor blades become 2 alpha. Find the ...
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5answers
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Which ball will hit the ground first?A ball simply dropped or a ball thrown across the room?

I've read that gravity doesn't affect an object's horizontal motion or vice versa, and some people told me that both balls will reach the ground at the same time. How is this possible, isn't that when ...
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1answer
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Why doesn’t a ball “roll” straight down the wall?

I conducted a physics experiment today. I simply held up a small ball against the wall, and let go. I was expecting the ball to exhibit some rolling motion of some sort due to friction, but to my ...
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0answers
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Sliding between three blocks kept on a smooth surface? [closed]

Here is how I tried to solve In the answer the mass of (md) is 3m but I am getting m. I have a conceptual mistake I am not getting it . Please help .
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On the performance of Bolt in the 100 metre sprint - solving equation of motion [closed]

I'm looking at the following article(1) in which a mathematical model is used to describe the performance of Bolt (in general of a sprinter) in a 100 m sprint. The equation of motion is $$ m\dot u = ...
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2answers
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Why Gravity doesn't affect Horizontal acceleration/motion?

It is still hard for me to grasp on why gravity doesn't affect horizontal motion, doesnt gravity causes a change in resultant force and thus cause a change in acceleration $F=m.a$