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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Will a tennis ball tossed straight up in a airplane cabin move towards the tosser or will its distance from the tosser remain the same?

If I am in a pressurized airplane cabin and I toss a tennis ball into the air, will the ball move towards me? My thinking is that though the ball is in an air bubble that is moving as a whole at the ...
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Distance and time contrasting results

I know the thing I am missing is right in front of my eyes, please help me see it, I see this equation $x_{final} = x_{initial} + v_{initial}t + \frac{1}{2}at^2$. I want to find the free fall distance ...
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Calculating the time to perform work on rolling shutters

I have rolling shutters, e.g.: I am trying to determine how much time it takes to raise/lower the shutters a specific amount. (Because of the physics involved, the time is non-linear relative to the ...
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What happens when a point mass reached Centre of Gravity of another body?

Suppose a body is slowly descending in a downwards firing rocket, in a tunnel dug through Earth's surface, and switches off the rocket just as it reaches earth's COG. Now since the body reached the ...
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2answers
79 views

How to calculate energy required to rotate a cube?

I would like to apply force instantaneously at point $F$ in the given direction on cube $A$ and have it rotate around point $C$ to end up in the same position as cube $B$. How would I calculate the ...
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If I saw two gears turning in front of me, how would I know which of the two has its own turn?

If I saw two gears turning in front of me, how would I know which of the two has its own turn? In other words, one gear rotates another static gear. How do I know which gear has its own movement?
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What does Newton mean by 3 kinds of centripetal force?

In his book "Philosophiae Naturalis Principia Mathematica", Newton writes in Definition V The quantity of any centripetal force may be considered as of three kinds; absolute, accelerative, ...
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How can we add torque acting at two different points? [closed]

How can we possibly add the torques acting at two different points?
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Why does ground reaction force decrease at the start of a vertical jump?

I don't understand why reaction force would decrease at the start of a countermovement jump. I've tried looking at this diagram and considering moments and how lowering the position of the center of ...
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4answers
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Why should angular momentum be conserved in this case?

Consider two disks (not friction-less) with some moment of inertia ($I_1$ and $I_2$). Both of them are given angular velocities ($\omega_1$ and $\omega_2$) both in same sense. Now if we bring both ...
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Spring block system on a rough surface [closed]

Suppose we have a given a block of mass m connected to a spring of spring constant k and kept over a rough horizontal surface having coefficient of friction u.Initially the spring is compressed by d (...
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2answers
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Theoretical question about velocity and acceleration

Imagine you have a ventilator that is spinning madly an creating strong air up force upwards. Then you put in the middle with a holder a paper ball. Then some-have detach the paper from holder. Sure ...
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Calculate ball speed and direction from forward angular speed and sideways force [closed]

I have a mounted arm with a ball attached to the end. It has a potentiometer that de-facto measures the angle between the arm and and the mount. below the ball is a newtonmeter (actually a weight ...
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3answers
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What do force extension graphs for springs show?

Say for example a 4N force is applied to a spring. The spring's restorative force will increase from 0N to 4N until the spring is in equilibrium. Throughout this time the resultant force acting on the ...
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Does static friction do work on an accelerating car? [duplicate]

I have seen several questions about this on this site and quora and there seems to be no definite, unanimously agreed upon answer. Does static friction do work on an accelerating car. Heres what i ...
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1answer
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Impulse by Tension [closed]

Suppose One end of a string is tied to a wall, and the other to a ball(mass $m$). Suppose the Ball is imparted a velocity which has two components: One away from the wall ($v_1$), and one ...
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Why does a ping pong ball bounce higher when it is dropped together with a cup of water?

Setup: an official ping pong ball is floating inside a party plastic cup filled with clean water, which is then dropped from a certain height onto a soft mat. Observation: the ping pong ball shoots up ...
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1answer
423 views

Calculate the magnitude of the acceleration due to gravity including its uncertainty?

I made a free fall time experiment and now I'm trying to make a report. The experiment consists of releasing a steel ball from various heights hi and measuring corresponding free fall times τi . ...
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3answers
537 views

How to make a object stay under water?

How to make an object submerged under water? Neutrally buoyant? Thank you
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1answer
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Reducing the line of collision of two rigidbodies while using the coefficient of restitution

I am trying to solve the problem of the collision of any two rigid-bodies. So far this is what I got: I am concerned with the part where I reduce the equation with the coefficient of restitution by $\...
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Is 13 really the answer for the “Devil's problem” in physics (a rolling tube with a rod)? [closed]

Recently I chewed the fat with a physics student and got intrigued by him mentioning "the Devil's problem," which he described as a simply worded mechanics problem that is extremely ...
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1answer
51 views

Coefficient of restitution for a perfectly inelastic collision

The coefficient of restitution is defined as the ratio of the differences in velocities of colliding objects after and before the collision: $$k_{COR}=\frac{v_{1,after}-v_{2,after}}{v_{1,before}-v_{2,...
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Alternative expression of acceleration in vector form

Let's imagine a one dimensional case, where a particle is moving with a velocity $v$ and an acceleration $a$. Thus $$a=\frac{\mathrm dv}{\mathrm dt}\tag{1}$$ Applying the chain rule, equation $(1)$ ...
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1answer
57 views

Normal force by String [closed]

Can, in any condition, the string or string-like objects provide normal force to any object getting supported by it? Maybe when the string is taut!!
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1answer
185 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
37 views

How to calculate the precise displacement of an object in projectile motion?

I am curious about how to calculate the precise location of a projectile. Assuming that acceleration due to gravity is $-9.81 \text{ms}^{-2}$, how would you calculate the displacement of a tennis ball ...
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3answers
59 views

Is friction different when viewed from a non-inertial frame?

I encountered this diagram when reading an explanation about why the front wheels of cars lift up when they accelerate. The diagram is in the reference frame of the car, so that there is a fictitious ...
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1answer
138 views

How to calculate bounce angle of disk from an edge

What I am looking for is how to determine the bounce vector of a disc hitting the edge of an object. The disc can be at any angle to the edge. I have a program that does the calculation without ...
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1answer
46 views

Air resistance and being negligible [closed]

I have a question, if I dropped a marble weighing $500$ grams or $1$ pound with a diameter of $5$ cm and the marble is a sphere how much time does it need to fall until air resistance is a factor in ...
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Can't astronauts use ball point pens in space? [migrated]

Is it true that astronauts can't use ball point pens in space? The mechanical contact of a ball point with the paper should make the pen write but I am not sure if it's true. Any clarification will be ...
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2answers
188 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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At what slope angle does walking uphill become more energy-efficient than cycling?

At what angle does walking uphill become more energy-efficient than cycling? To me cycling uphill feels harder than walking uphill, so I wonder at what slope-angle this happens. Two other ways to put ...
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1answer
62 views

Pendulums in inertial and non-inertial frames

If I have a non-inertial frame accelerating with acceleration $A$ with respect to an inertial frame and if I have two pendulums, one in the inertial frame and the other in the non inertial frame, then ...
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1answer
191 views

Energy density and inernal density relations

If energy density relates to rest mass density as $\epsilon = \rho / c^2$. How internal energy relates to energy density? Also, when do we write $\epsilon = \rho / c^2$ an when $\epsilon = \rho / c ^2 ...
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3answers
60 views

In which direction will the friction act?

Suppose a block of mass $1$ kg is kept on a rough horizontal surface. Let the friction coefficient be $0.2$. Now let's say, I apply a force of $1$N in the east direction. Friction will act in the ...
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1answer
49 views

How does waves transfer energy forward

I'm teaching a O-level physics student (grade 10th). We were talking about waves and she asked this question, how does waves transfer energy forward if the molecules just moving up and down? How does ...
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1answer
46 views

Energy and momentum transfer before and after breaking a light string [closed]

Imagine two masses are connected by a light string, which then snaps - how does this change the speed of the masses? My understanding so far is that the average speed of the two masses is unchanged $\...
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2answers
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Friction during ball backspin and overspin

I already know sliding friction of ball on a flat table and rolling resistance of it. How do I know coefficient of friction value when the ball has backspin with some angular velocity $\omega$? And ...
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2answers
162 views

Power in different reference frames

I would like to reopen the question asked in this post because I am not quite satisfied with the accepted answer. Imagine observer A stationary (in world reference frame) and observer B moving with ...
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1answer
40 views

Work done by internal forces: when and why is it 0?

When exactly is the Net work done by internal forces on a system 0, and what is the intuition behind it? I have heard it is valid for rigid bodies but I am unaware of what they are as of this point, ...
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1answer
80 views

How do I analyse this pulley-trolley system? [closed]

"find a force F such that the blocks are stationary relative to the trolley. All surfaces, wheels and pulley are assumed to be friction-less" 1: This is a very common mechanics problem and ...
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COM of rope hanging between 2 pegs [closed]

I want to find out the COM of a rope hanging between 2 pegs as shown .The mass of the rope is m and the length is l.
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4answers
86 views

Describing forces in rolling

Consider a wheel on a frictionless horizontal surface. If we apply a horizontal force (parallel to the surface and above the level of the center of mass), what happens to the wheel? Does it roll or ...
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3answers
353 views

Why does it take different levels of effort to lift two objects with the same mass?

Suppose we have two different objects, one denser than the other. In short, what I mean is that one object is bigger than the other but they have the same mass. Now why does it take different efforts ...
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4answers
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Can potential energy be treated as vector quantity?

Force can be representd by potential energy function which for 1 dimension case satisfies the derivatives condition $f(x)=-d U(x)/d x$. If we now consider 3D space, then position will now depends on ...
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3answers
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Will the tension be the same throughout a massless rope?

If a mass is suspended from the ceiling by a massless rope, will tension be the same at all points on the rope?
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1answer
31 views

Why does a bike skids on the sand?

Whats the theory behind bike skidding on the sand? Is it related to friction and if then why it skids. Is that the sand has more friction if so then pedaling should be difficult rather than skidding.
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197 views

Newton's 2nd law for rolling motion with changing moment of inertia

While writing an answer to this question, I encountered a puzzling conceptual problem when applying Newton's second law for rotation about an instantaneous axis of rotation when the moment of inertia ...
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1answer
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Gravitational attraction between two objects of non-uniform mass-density

Is there a formula to calculate the gravitational force of attraction between two bodies - both are suspended in 3D, both have a non-uniform mass density, both are closed geometric shapes in 3D, and ...
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What accounts for the flow of liquid, Net force or Net Pressure? [duplicate]

Consider a tube having liquid kept on a horizontal plane. Now suppose two forces of unequal magnitude act on the two open surfaces of the liquid, such that area of one surface is greater than the ...

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