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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Amplitude of Shm if Constant External force is applied

In the attached picture, is the spring mass system in equilibrium with a constant force $F$? My question supposes that the system is slightly displaced from equilibrium (let's say to the left). Is ...
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5answers
106 views

Is net work always equal to the change in kinetic energy?

I know that $$W_{net}=\Delta K\tag{1}$$ However, I don't know if this is only true in a system where only kinetic energy is present, or if it's also true for a system in which there's potential ...
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Example of anisotropy frame of reference

I have studied that an inertial frame of reference is the one that is homogeneous, isotropic and time-independent. For instance, a reference frame on a rotating wheel is not an inertial frame of ...
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42 views

Rotation of Rigid body

How to prove the equation (4.14) $$ a_{ij} a_{ik} = \delta_{jk} $$ from the equation (4.13) $$ x_i' x_i' = x_i x_i $$ With summation convention I found it very easy. But, using summation I am not ...
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Visualizing Physical Units in Phyiscs

I do best in physics when I can make sense of the units that accompany values, and I do this by visualizing in my mind what is happening. Take for instance, $v=\frac{s}{t}$. When I think of velocity I ...
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Dynamics of Gyroscopic P recession

It is taught relatively early in classical mechanics that the precession of a top exists because when the body is spinning, the gravitation torque pushes the rotational axis (more accurately it pushes ...
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2answers
689 views

Falling book and paper

I've seen an experiment where a closed book with a piece of paper lying on its cover is dropped a short distance (the piece of paper is smaller than the book; the book's cover is parallel to the Earth'...
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3answers
512 views

Question on work, energy and power

The engine of a train is working at a constant rate. The maximum speed of the train up a certain incline is $V_{1}$ and the maximum speed down the same incline is $V_{2}$. Then if the train moves on a ...
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Did Newton already have $F = ma$ (or equivalent) before finding his gravity equations?

Newton's gravity equations are in an F = ma configuration. Multiply the acceleration formula by m, you get the force formula. So did he have F = ma (or some equivalent - I think the concept of ...
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Can conservation of momentum be applied before and after a particle is acted on by a force?

Suppose a body is moving with a velocity of $v_0$, and then a force acts on it for a certain period of time, after which the velocity of the body changes to $v_1$. Can be the conversation of linear ...
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Where can pseudo-force be used?

I was doing this question and eventually got the answer but I had a thought :- It being a non inertial frame , can we apply pseudo force on it? But as the question says both are travelling with ...
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1answer
181 views

Joule heating for a fluid

Say you have a conductive liquid with a changing magnetic field going right through it, causing an electric current. How exactly does the electric current travel and how could you calculate the ...
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1answer
247 views

How Does the Electron Detector Detect Electrons? Dbl Slit

The double slit experiment is famous for the electron acting like a particle rather than a wave when observed. Is it the case that the nature of the detection apparatus rather than passively taking ...
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Do I do zero net work if I start and stop a spaceship in vacuum?

As question states, I start and then stop a spaceship in vacuum by using orientable thrusters. In the acceleration phase, I am doing positive work, but in the deceleration phase I am doing negative ...
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Moment (torque) problem [closed]

Why in this figure the total torque on object is not zero as one force cause the object to move in clockwise direction and the other force cause the object to move in anticlockwise direction ? How ...
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How does a balancing toy work?

I know that the balancing toys have their center of mass under the axis on which they are balancing. That's why they stay still. But when we give a little tap on it, it re-balances itself. But how ...
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1answer
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Dynamics of a rotating coin

Sometimes when I'm bored in a waiting area, I would take a coin out of my pocket and spin it on a table. I never really tried to figure out what was going on. But, recently I wondered about two things:...
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What force stops a car?

I've been doing physics problems regarding cars for a while. I understand that there is a static friction (which appears when the wheel is rolling) and kinetic friction (which appears when the wheel ...
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Energy conservation in Elastic collision

A question from my textbook is stated below In an elastic collision The initial kinetic energy is equal to the final kinetic energy The final kinetic energy is less than the initial ...
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1answer
70 views

Pseudo force is a mysterious new force of unknown origin because of wrong coordinate system?

Consider the following paragraph. That is, since Moe’s coordinate system is accelerating with respect to Joe’s, the extra term $ma$ comes in, and Moe will have to correct his forces by that amount ...
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1answer
44 views

Braking systems on cars

I thought of a maths problem for myself to solve, as it seemed like a good problem to try to get my head around. My issue is that I got stuck at the first hurdle. I was reading up about the braking ...
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Does the streamline at the top of the wing have the same curvature as the curve at the top of the wing? What does the difference mean?

As shown in the figure, my question is that Curve A (Wing Top Curve) and Curve B (Streamline) are not equidistant curves. Why is this, and what does it mean for lift generation?
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Having some tension about the Tension in Atwood's Machine

I was thinking about how the tension force is equal in a massless String. While the explanation that the String would accelerate crazy, crazy, crazy fast if there was an actual difference makes sense, ...
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1answer
125 views

Infinite string attached to a spring [closed]

I'm trying to solve a problem related to waves on a string. Say I have an infinite string, with tension $T$ and mass density $\mu$. To the string, at $x=0$ (seeing as it's infinite, the specific ...
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Unbalancing equal weights on a scale

If two equal weights are kept on a swing, is it possible to unbalance them by applying only a horizontal force on the swing in such a way that the sawing starts accelerating? If we look into it ...
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1answer
232 views

Physics of Sound and the middle ear?

Once sound waves reach the eardrum, ,the eardrum moves back and forth and transmits those waves/pulses to three bones that serve to transmit and amplify the pulses to another "drum" in the inner ear. ...
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Questions about isolated systems and conservative vs non-conservative forces

Is it correct to say that mechanical energy will always be conserved in any conservative system (a system with no non-conservative forces), no matter if it's isolated or not? Are there any examples of ...
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Throwing something into orbit [duplicate]

is it possible with newtonian gravity to throw something (which has no on-board propulsion) so that it will orbit the earth without colliding with it(friction is not present)? my intuition tells me ...
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2answers
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Gravitational force on point mass due to uniform rod

So we have a uniform rod of mass M and length L and we have placed a point mass of mass m, which is distance a away from the midpoint of the rod. Now setting the coordiates axes to work with, I put ...
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3answers
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Why is mass totally neglected when center of gravity is shifted? [closed]

A square sheet of metal has a square of one quarter of the original area cut from one corner as shown in the figure. Which of the following statements is true about the position of the centre of ...
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1answer
162 views

Gravity assist, Coordinate system transformation

I am currently learning about the physics and the mathmatics behind gravity assist. I have a question regarding the coordinate transformation between the planet frame and the sun frame. I want to ...
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1answer
86 views

Mathematical Model for a Pendulum in an Electric Field

I am studying Higher Level Physics and for my Physics IA I am doing an experiment determining the effect of the voltage between two parallel plates on the on the frequency of a pendulum in between the ...
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2answers
38 views

Force applied on a massless pulley

Hi guys I had a question regarding this diagram. My teacher told me that $$F-2T = 0$$ Hence,$$F=2T$$ but I am confused that shouldn't it be:-$$F+2T=0$$ and hence, $$F=-2T$$ (Considering pulley to ...
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Question about a crate in an accelerating truck and friction force

"A crate is sitting in the center of the back of a flatbed truck. As the truck accelerates to the east, the crate moves with it, not sliding on the bed of the truck. In what direction is the friction ...
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269 views

How is it possible that momentum is conserved but kinetic energy is changed? [duplicate]

A simple maybe 8th or 7th grader question, but I can't really get over it. Elastic collision: momentum is conseved and so is the kinetic energy whereas in an inelastic collision, momentum is conserved ...
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2answers
118 views

Is the total momentum of the ground and a ball that bounces vertically up the ground conserved?

The distance that a ball reaches after it bounce is less than the height from which it was dropped. So $$m_1v_1 + m_2v_2 \neq m_1v_1' + m_2v_2'$$ Where: $m_2$ is mass of earth $v_2$ is initial ...
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73 views

In zero gravity!

If spacecraft moving in a stable speed or acceleration suddenly stopped would an astronaut continue moving forward (such as a man in a train) ?
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The physics of airplane flight [closed]

Physics in schools teaches two contradictory and mutually exclusive things: (1) That the upward lift force on an airplane in flight equal its weight (Lift = Weight = mass x gravity). This is based on ...
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3answers
136 views

The traces of homogeneity and isotropy in Newton's system

I know that Lagrangian system is required to demonstrate the relationship between homogeneity(or isotropy) and conservation. Is any expression or equation pertaining to the homogeneity of time and ...
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1answer
45 views

Can a spinning ball bounce off the floor without slipping?

Suppose a ball is dropped vertically downward, but it also given some spin along a horizontal axis. Then when the ball bounces, it will presumably pick up some horizontal velocity. Is it possible for ...
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Dynamics subject to an alternating step/rest sequence with two different resting intervals

Consider that a particle is either in motion (with velocity $u$) or at rest: $$ \dot{x}(t) = u S(t) $$ where $S(t)$ is a switching process between $0$ and $1$. This switching is defined as follows. ...
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169 views

Why are springs shaped the way they are?

Why are springs coiled the way they are? Why not some other shape? Is the shape due to its elasticity or something?
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When is tension inversely proportional to acceleration?

So I have questions where 2 pulleys are present, and when one of them is fixed to a rigid support on one end, it is said that tension is inversely proportional to acceleration. On the other hand, ...
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1answer
162 views

How do I know whether members are in tension or compression when using Method of Sections?

So we started doing structural analysis in my engineering class lately, and are doing trusses. However, I'm not quite sure how method of sections works conceptually. I'm getting the right numbers, but ...
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4answers
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Force = Mass ⋅ Acceleration [duplicate]

I have a doubt on the formula, $$F=m\cdot a$$ In pushing the wall, as per formula, $F= m\cdot 0=0$ as there is no acceleration hence zero. Therefore force become zero. But we have applied some force ...
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2answers
30 views

Difference between centre of mass of ring and solid sphere

Centre of mass of ring and centre of mass of solid sphere is at the geometric centre but how the mass of ring will be less than the mass of the solid sphere? And centre of mass depends upon mass, so ...
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2answers
148 views

Proportional acceleration due to changing density of the Earth

My question has to to do with a recent video Minutephysics posted about the time it takes for a person to fall through the earth, found here http://www.youtube.com/watch?v=urQCmMiHKQk At around 4:05,...
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Why are springs spiral-shaped? [duplicate]

I've had this question on my mind for quite a while and looking at the web, I couldn't find an answer to this question. I've had a lot of physics experiments involving springs, unintentionally ...
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4answers
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How exactly is a normal force exerted, at the molecular level?

I've been surfing the web for quite a while, finding the answers I would need, but couldn't find a convincing one. First of all I need to remind you that this a very long/continuous question, so ...
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1answer
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Did the book principles of physics by halliday solved this question correctly?

I like your forums and thank you for being helpful. It's the first time for me to post. Attached is a question from Chapter 7, Principles of Physics by Halliday. I'm not actually convinced with their ...