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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Relation between force and torque for a set of gears/bicycle

If there are 2 gears meshed together and they are of different sizes, then rotating the smaller one will make the larger one spin with a smaller angular velocity but with more torque. And the opposite ...
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52 views

Boundary behaviour of a mechanical wave

Let us assume we have a taut rope and I introduce a pulse in it by whipping one end. Now if instead of a clamp, I have tied the other end of the rope to a denser rope, a part of the energy is ...
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101 views

An intuitive explanation regarding propagation of mechanical waves

I was studying mechanical waves today and have questions regarding how a pulse is propagated on a string and its reflection and transmission at a boundary and I hope I can find help here. First, ...
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126 views

How does a cyclist moves the center of mass of the cycle-cyclist system?

Consider the image shown below, In the left diagram the centre of mass of the system lies upon the perpendicular from the point of contact. But in the right diagram the centre of mass has shifted ...
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98 views

What is the difference when we measure torque/angular momentum about a point and about an axis?

When do we measure torque about an axis and when do we measure torque about a point?Whats the difference? I tried searching this on google but did not get satisfactory answer.
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38 views

Why do linear momentum and angular momentum have to be conserved in ground frame only?

According the Newton's second law of translational and rotational motion respectively if the net external force /torque acting on a body is zero then the linear/angluar momentum is a constant . So ...
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247 views

If a bullet were to hit a target point blank, would the force upon impact be the same force as the recoil?

When a bullet fires from a gun the force exerted on the bullet by the blast is equal and opposite to what you feel as the recoil. I know that acceleration on both the gun and bullet is different due ...
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49 views

Motion of projectiles

I was reading Feynman's lectures about the law of gravitation and came across this experiment: Assuming vacuum, if the ball that was shot horizontally was shot so that it would land at a location $...
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494 views

Max extension of spring mass system

While attempting problems of simple harmonic motion I came across this problem, which has gotten me confused. A fixed horizontal spring is stretched by a constant force $F$. I am required to obtain ...
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46 views
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52 views

Angular Momentum

I have several questions about angular momentum. 1.I know there are 2 parts of angular momentum - translational and rotational. For a body with respect to a fixed point, translational angular ...
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1answer
55 views

Simple frame of reference problem (conservation of momentum?)

I'm having trouble wrapping my head around a particular concept. Suppose we have a machine that fires balls of speed $u$ at some mass rate $\sigma$ (of units $\frac{kg}{s}$) directly at a car of mass $...
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193 views

Rotation of a cube around its diagonal axis

I have the following multiple choice question that I am attempting to answer: For B1.3, (a) appears to be the most logical choice. It is my understanding that an object whose shape is asymmetric ...
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2answers
158 views

Angular momentum about a moving axis

How can we define angular momentum of a system about an axis that moves parallel to itself? For example Axis passing through CM that is perpendicular to plane of body. When we talk about ...
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46 views

What is required for a time-varying moment of inertia matrix?

Let me preface this question by stating that I am familiar with euler's equations for rigid body dynamics, torque and angular momentum. Despite the math, I'm still a little fuzzy about certain ...
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2answers
200 views

What happens if a motorcycle going at 50mph crashes head into a car going at 60mph? [closed]

I wonder if a motorcycle (going at 50mph) crashes into a car (going 60mph), what is the damage that motorcycle will experience? Here's a diagram that shows what I've in mind: ...
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26 views

How to show that the configuration space of two beads on a rod is a triangle?

I do math, and this problem showed up in the setting of translation surfaces. Lets say we have two beads of masses $m_1$ and $m_2$ on a rod of length $a$, with $m_1$ on the left of $m_2$. Denote ...
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1answer
86 views

circular motion relative velocity question

You are standing in the middle of a disk of radius $2\:\mathrm{m}$ rotating at $\pi\:\mathrm{rad s^{-1}}$, and there's a smooth puck at $1.5\:\mathrm{m}$ away from the centre. If the puck was released,...
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65 views

If, for a body rolling on an incline, the friction coefficient isn't enough to allow pure rolling will it still roll?

More specifically that it won't be pure rolling (obviously) but would it still have some rotational motion along with its translational motion? (if yes how would we write their mechanical equations). ...
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182 views

Deduction of Lagrange's equations for non-conservative systems using Hamilton's Principle

Consider $\vec{F}$, as the total force applied on the system, $U$ the potential energy of the existent field, and $\vec{Q}$ a non-conservative force. We have that: $$F_k=-\frac{\partial U}{\partial ...
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34 views

When applying the equation of torque and equating it to $I\alpha$ which moment of inertia do we take?

I believe $T=I_{cm}\alpha$, where $I_{cm}$ is the moment of inertia about centre of mass and $\alpha$ is the angular acceleration. But do we take $I_{cm}$ even if the torque has been taken about a ...
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4answers
71 views

Must one include friction and gravitational force in the work term?

Example problem: "A sled has an initial velocity up a ramp of 5 m/s, the ramp has an angle of 20 degrees to the horizontal, and the coefficient of dynamic friction between the sled and the plane ...
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2answers
85 views

Simple model that explain the flow of electrons in metals

I am not quite clear about how electrons (negative electric charges in general) flow through a metal. I imagine the metal as a lattice of small positive charges $+q$ that can not move and the - and + ...
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243 views

Bead on a smooth rotating rod

Suppose a bead ($m$) is free to move on a thin rod in the otherwise empty space. The rod is made to rotate at constant angular speed $\omega$. Lets assume the initial position of the bead is $(r_o, \...
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151 views

Accelerated pure rolling and friction

I know that if a body is pure rolling with no acceleration then friction acting on it is zero. But what about if the CM has an acceleration? Then can we say that friction is present? Suppose that ...
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1answer
104 views

Who told us how to measure torque?

We all know that force and torque are physical quantities which we have defined according to our purpose of work. Now we are all aware that Newton's Second Law from his Laws of Motion states how to ...
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58 views

System of potential energy

Is potential energy calculated between a system? More specifically, if we say 'potential energy of a ball with respect to earth', does it mean that the Earth + the ball is a system?
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118 views

Conservation of Mechanical Energy Before and After Impact of a Hammer

If a hammer does work by driving a nail into a wooden board, how does the mechanical energy from right before the hammer hits the nail compare to the mechanical energy after the nail has been driven ...
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168 views

How can one conclude upward force is related to tension in this question?

In preparation for the SAT Physics Subject Test, I have been doing extra practice problems. This one states: A garment bag hangs from a clothesline. The tension in the clothesline is $10 \,\text{N}$ ...
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57 views

Mismatch between underdamped and critically damped solutions

If you have a harmonic oscillator with damping $D$ (e.g. small angle pendulum) $$\ddot{\theta}+D\dot{\theta} + \theta=0$$ then the solution I get in the underdamped case ($D^2-4<0$) is: $$\theta=\...
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23 views

how to reduce the order of the hamiltonian equation for electrical problem given below?

I am having my FYP in this Hamiltonian project to analysis the integrator for Hamiltonian system. Can anyone please guide me how to reduce the equations to first order using substitution method?
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1answer
138 views

Why is it easier to pull a lawn roller rather than pushing it?

Does it have something to do with friction or weight distribution in pulling is favorable or anything else ?
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69 views

How do forces affect work? [closed]

I was doing my homework and I came across the question: Suppose that two objects, each with the same mass, are accelerated from rest to the same velocity. The force that accelerates one object ...
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1answer
99 views

How is this seemingly counterintuitive result in a rotation problem explained?

In the classic spool problem, where a spool of string of mass M is unrolled with a force F, like in the diagram, after working through the equations with Newton's laws of rotation and translation, we ...
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107 views

Magnitude of tension in a bent string

I understand tension in a straight string as a reaction force to a weight, which acts along the string, ultimately resulting from the attractive forces between the constituent particles of the string. ...
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81 views

Are some laws in physics really as simple as they seem?

For example, is $F = ma$ really an exact formula, or is it an approximation? I know a lot of formula's come from taking the first few terms of a Taylor expansion, so I was wondering if the simple ...
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1answer
417 views

Tension in string question [closed]

Problem: A 12.0-kg box resting on a horizontal, frictionless surface is attached to a 5.00-kg weight by a thin, light wire that passes without slippage over a frictionless pulley (the figure (Figure 1)...
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66 views

string applying a force on pulley

Why should string apply a force on pulley?(like atwood machine cases)and does that mean the pulley will exert an equal force on string(newton's third law)? Please explain in detail,if possible ...
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1answer
51 views

Please help me with this doubt from center of mass concept

Take the case of Atwood machine where masses of blocks are $m$ and $2m$. The acceleration of individual masses are $\frac g3$. now the acceleration of center of mass of masses and string system is $$...
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3answers
94 views

Does an object decelerate when reaching terminal velocity

I'll take the sky diver example. Right when a sky diver jumps out of the plane the net force of the diver is greatest. Then the diver begins to reach terminal velocity where the force of resistance = ...
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1answer
68 views

Time spent in eclipse of an object

Well consider an orbit - I'm trying to calculate the exact time spent in the shadow of the body you orbit around. An explanation of "shadow" (sun is positioned to the far left): For a circular ...
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3answers
144 views

Why do objects move when you apply a force that's equal in magnitude to the friction? [duplicate]

If the friction on an object is 200 N and you apply 200 N, it seems, the forces should immediately cancel each other out since the friction and your applied force go in opposite directions, leaving ...
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1answer
84 views

Why is friction not dissipative in rolling motion? [duplicate]

We know that non-conservative forces like friction is a dissipative force. But according to my book when a solid cylinder is rolling down a rough inclined plane of inclination angle $\theta$ the ...
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3answers
134 views

What is the distance between two objects in space as a function of time, considering only the force of gravity? [duplicate]

What is the distance between two objects in space as a function of time, considering only the force of gravity? To be specific, there are no other objects to be considered and the objects in question ...
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2answers
80 views

Why does Goldstein's derivation of orbits from Newton's law not yield the orbit consisting of symmetric oscillation along a line thru center of Sun?

Why does Goldstein's derivation of Keplerian orbits from Newton's law of gravity not yield the orbit consisting of symmetric oscillation along a line passing thru the center of the Sun? The fact that ...
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5answers
370 views

Pushing down on the gas pedal of a car a good example of jerk?

I'm trying to think of the clearest examples to demonstrate the concept of jerk to a layman. Ignoring drag and making other reasonable assumptions (friction is conveniently there to only allow you to ...
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1answer
40 views

Conservation of momentum in inelastic conservation

Why does momentum and velocity change along contact normal but not contact tangent In in elastic collision? Suppose a ball strike an inelastic surface. It's velocity component does not change along ...
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2answers
82 views

Roller Coaster Physics

I am trying to figure out how to calculate the $g$-forces throughout a non-uniform corkscrew as well as the exiting velocity. Do you calculate each radius separately and each $g$-force separately ...
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139 views

Defining gravitational potential

I recently came across the definition of gravitational potential where ..... Suppose a particle of mass $m$ is taken from a point $A$ to $B$. Let $U(A)$ and $U(B)$ denote the gravitational ...
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1answer
139 views

Confused by gravity and weight [closed]

I know that $F = mg$ so $2,00 \textrm{ KG m} \cdot 9,81 \textrm{ N g} = 19,62 \textrm{ N F}$ Why does my book say that the weight of a $2,00 \textrm{ KG}$ object is $19,62\textrm{ N}$, the mass is $2,...