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448 views

Why we can't jump without bending our knees?

I observed it while trying to jump from my bed with my knees straightened and I failed to do it. I want to ask whether it is with all of us our it may be a medical issue with me? Why we can't jump ...
146 views

Why does the universe require relativity? [closed]

Are there any known compelling reasons why our universe is governed by relativity instead of Newtonian physics? I recognize that an infinite $c$ would be a problem, so I'm not asking about that; I ...
128 views

Why coordinate axes are perpendicular to each other?

Coordinate axes are chosen to be perpendicular to each other because it is convenient, calculations are easier. This is what I have read. But in case that coordinate axes are per example 60 degrees ...
113 views

Why doesn't a force perpendicular to the direction of motion change the speed?

It changes direction but not speed and this is proved in experiments. But is there any more "deep" reason as that space has isotropy and energy must be conserved per example?
65 views

Mathematically equivalent physical systems

This seems a bit different than the typical question here, but I'm not sure where to ask. Is there a name or field of studying mathematically equivalent systems? The simplest example I can think of ...
51 views

Why do physicists comes up with special names for change in quantities? [closed]

I only have a basic understanding of physics, so this may be a naive question. I've noticed in my self-study that when referring to the change in some quantity $Q$, instead of just calling it change ...
78 views

Note and homework organization [closed]

I am currently in a mechanics class and have some trouble trying to figure out how I should structure my lecture notes and my homework. I recently began rewriting my notes after class but I am still ...
77 views

Is there a way to study mechanics without having to rely on free body diagrams?

For example, consider a very simple situation often used as example in teaching: a horse pulling a stone through a rope attaching them. The analysis goes something like this: There is a force exerted ...
121 views

State of academic fields of analytic mechanics and Multi Body Dynamics (MBD)

My question essentially contains two parts: one practical question and one philosophical question. Background I am an engineering student working in the field of Multi Body Dynamics (MBD). My ...
83 views

This is quoted from A.P.French's Vibrations & Waves. Explicit differential form of linear harmonic oscillator is:  m\dfrac{d^2x}{dt^2} + kx = 0 \quad \& \quad \dfrac{1}{2} m(\dfrac{dx}{...
56k views

Forces on a ball thrown upwards

When a ball is thrown up in upward direction, it is said that force is in downward direction. Why we don't we consider the force given to the ball to throw up in the upward direction? Is there is no ...
189 views

Newton's Principia: Astronomical prerequisites?

I am planning to read the Principia but I currently have no knowledge about Astronomy. What astronomy prerequisites do I need to understand the Principia? I would prefer older books (or "treatises"), ...
436 views

What is this simple mechanism called? [closed]

I often build with Lego and use this mechanism: It converts the rotational movement to linear by making the stick between the two blocks go back and forth. What is this mechanism called?
2k views

What really is “inertial force”?

In Fluid Mechanics we often see the term inertial force when discussing Reynolds number. The problem is, I didn't really get what's this inertial force. Basically, the notion of inertia I have is that ...
49 views

Will the usage of Exo-Skeleton Gear actually weaken the human body over time? [closed]

As we all know, Exo Skeletons as they exist now are just a series of Force multiplying apparatuses working together, also the human body changes to accommodate environment specific factors in order to ...
646 views

Prerequisites for Halliday Resnick Walker

I am in grade 10. I have developed an interest in physics but unfortunately I do not know/ have not studied calculus yet as my school board does not recommend it in grade 10. I have a copy of ...
634 views

Naming vectors in free body diagrams

Is there a convention for naming the vectors? Suppose there is a box on a table. I'm going to draw the forces acting on the box. So I focus on the box and ignore forces acting on the table, the ...
83 views

If the axis of rotation is fixed, is it ok to say clockwise torque?

I know that the direction of torque is along the axis of rotation, but would it be acceptable to say, for example considering a vertical thin rod in the x-y plane with a force acting on the bottom end ...
96 views

How far do atoms move in a wire when whirling it horizontally? [closed]

so the question is: I whirl a mass m attached to a wire with length L and diameter d around my head in the horizontal plane. The mass takes t seconds to move around a circle. How far do the ...
100 views

I know there are a lot of variables that affect how quickly this would occur. Any information on the topic would be highly appreciated. For sake of argument, lets say 1 square foot chamber, lets say ...
617 views

Motorbike with parachute vs normal skydive

Had a strange discussion in the coffeeroom today. The background was a story about a guy that took his motorcycle to transport himself to the airstrip to do a skydive. Since there is no place to put ...
107 views

Book recommendation [duplicate]

I already learned the Physics' basics like Newton Laws, Electricity, and Optics. Can you recommend me a good book for advancing with my learning of physics(with some math)?
97 views

Orbital motion (Mechanics) [duplicate]

I am a student in Mechanical department and I took today a lesson with a title of Orbital motion. I need a good mechanics reference that discusses this topic.
158 views

Does a fundamental principle require specific concepts? [closed]

The angular momentum principle is a fundamental principle. So it can explain a large variety of phenomenon. Doesn't it need concepts like center of mass also for explaining phenomenon? Or just the ...
78 views

Helping/explanatory notes for Landau&Lifschitz Physics Course [duplicate]

I've recently restored my interest on theoretical physics (I have a master degree in Electrical Engineering) and began my study with first volume of the Physics Course by Landau and Lifshitz. This is ...
979 views

Correct terminology for combined kinematic and dynamic state

The kinematic state is defined as the position and orientation in space. The dynamic state is defined as the associated velocities. What is the correct terminology for the combined kinematic and ...
499 views

Does the slip-stick phenomenon have any application?

The slip-stick phenomenon is present all around us, be it the noise of car breaks or in earthquakes. But does it have any real-life application?
2k views

Meaning of the word “Moment”?

This question is more of a question about the origin of a physical term moment used in many contexts. My question is about the linguistic or historical meaning of the word "moment". Please don't ...
974 views

Explanation for classic mechanics puzzle

I'm trying to figure out a nice way to describe to a kid the physics behind these experiments: Assuming ideal conditions, we have a small boat with a sale, close to a lake's shore and a fan fixed on ...