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1answer
48 views

Different forces from different inertial frames?

I've been having trouble understanding this equation here derived in the picture given below. If I change reference frames to one which is moving at a velocity u with respect to the first frame, then ...
-1
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0answers
72 views

Is there a flaw in Newton's first law? [on hold]

When there is no external force, the object can move in a straight line or rotate around its own center of mass in a uniform manner. When there is no external force, the object does not necessarily ...
0
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1answer
39 views

Interaction between various forces, by which one is to calculate an angle?

I am new to Newtonian mechanics, and was wondering about the following question. I basically have the ingredients for the answer, but I cannot seem to find the way to put this together into one ...
1
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0answers
35 views

Validity of Newton's second law in a non-inertial reference frame

Suppose two observers are mutually interact through gravitational force (assuming they are alone at space). If the reference frame is fixed in one of the observers could the observer in the reference ...
0
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1answer
68 views

What do you mean by Newtonian space? [closed]

What do you mean by Newtonian space? When you see this question, most of you might be thinking that I am trying to crack a joke or something..but no. This was a genuine doubt which one of my friends ...
1
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1answer
104 views

Are there 2 laws of motion or only 1?

It seems clear that Newton's first law is a special case of his second. Although perhaps people might argue that it emphasizes the centrality of inertial frames. But is the third law also just a ...
0
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2answers
70 views

Isn't inertia experience by person in moving bus same as torque

When a bus moves suddenly, the person standing in it tilts backwards. This concept is explained using inertia(tendency of body to resist change in its state of motion) but when the bus moves suddenly, ...
1
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1answer
26 views

When do we illustrate inertial forces on inertial frames of reference?

I came across two practice questions wherein an object was attached to an accelerating vehicle, yet only one of these cases required an inertial force to be illustrated on the object's free body ...
0
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1answer
34 views

Question on force invariance under the Galilean Transformations (GT)

By the Galilean transformations, one can easily derive that two different inertial observers 1,2 always measure the same forces. That is: $$ \vec{F_1} \ \left(\vec{r_1}, \frac{d\vec{r_1}}{dt_1},t_1\...
0
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2answers
86 views

Is force really defined by the second axiom of Newtonian mechanics? [duplicate]

Many people claim that force is defined by the second axiom of Newtonian Mechanics, which is: "In an inertial reference frame, the rate of change of momentum of a particle equals the sum of the ...
0
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1answer
65 views

Is it correct to use Newton's third law on all these scenarios? [closed]

So I was thinking about Newton's third law for sometime lately, and my problem is more about the concept, I'm fine with solving problems. I thought of these scenarios and tried to apply Newton's three ...
0
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1answer
103 views

Inertia when pulling on a rope [duplicate]

Imagine a fragile cord attached to a ceiling with its other side attached to a sphere. On the lower part another cord is atrached to the sphere. Now visualize you pull STRAIGHT downward on this cord. ...
0
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1answer
103 views

What happens if the moving frame in special relativity is non-inertial?

We have the lorentz transformation equations for relating inertial frame of references. What will the transformation equations be if the frames are non inertial? Is there any "pseudo-force like ...
2
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5answers
443 views

If centrifugal force isn't real then why am I being pushed on a merry go rournd? [duplicate]

I just finished my class on circular acceleration and I learnt that centrifugal force (outward force) is a psuedo force. It doesn't really exist. Now suppose I am going round in my car or a merry go ...
2
votes
2answers
225 views

Acceleration in a rotating frame

From "Centrifugal force", Wikipedia: Acceleration [...] By applying the transformation above from the stationary to the rotating frame three times the absolute acceleration of the ...
0
votes
1answer
93 views

Why do some objects not move when there is no external force while others move at a constant velocity?

Newton's first law says that an object remains at rest or moves at a constant motion if there is no external force. Why do some objects remain at rest, while the others move at constant motion?
0
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1answer
58 views

Does Newton's third law apply in inertial frames of reference?

My textbook mentions that one of the properties of an inertial frame of reference is that Newton's first law must be valid in it. I'm a bit curious because it only mentions Newton's first law and say,...
-2
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1answer
86 views

Lorentz Covariance of the law $\mathbf{\vec{F}} = \frac{d\mathbf{\vec{p}}}{dt}$

This is the force law as seen in some frame $S$: $$\mathbf{\vec{F}} = [\gamma_v^3 ma_x, \gamma_v ma_y, \gamma_v ma_z]$$ How do I Lorentz transform it to: $$\mathbf{\vec{F}'} = [\gamma_v'^3 ma_x', \...
-1
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2answers
54 views

Confusion understanding total external contact forces on a rigid body

As I know, Newton's third law states that "forces occur in pair between two bodies,a pair of equal and opposite forces on each other and Net force on a system of particles is equal to total external ...
0
votes
4answers
109 views

What is the actual reason for the effects of fictitious forces? [duplicate]

Suppose a person is standing in a bus moving with constant velocity. Assume that static friction between his feet and bus surface is very low (you could assume he is on roller skates) and we are ...
-2
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1answer
114 views

Inertial Force Vs. Weight

What if, while coming down in an accelerated elevator, the inertial force acting on us is greater than our own weight? Would we fly upwards?
0
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1answer
203 views

My question is about the ommision of pseudo forces when we draw the free body diagram from an inertial frame of reference

I have this question, in my physics book where a bob attached to a string is in a slanting position as it is inside a cart moving forward with an acceleration. I understand that if we draw the free ...
0
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1answer
47 views

Force seen by an observer traveling near the speed of light

Suppose there is a wind with velocity $v \ll c$, which is blowing on a person who is moving at velocity $u \ll c$ (both in the $x$-direction). In the rest frame of the person, the wind exerts a force $...
4
votes
1answer
807 views

Does force definition depend on frame of reference?

Let’s assume we have 2 different observers. Observer 1 sits in space and observer 2 sits in a space lab which is in a free fall state toward the Earth. We further assume that observer 2 in the space ...
1
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1answer
325 views

Statement of the first law of motion and definition of force [duplicate]

Newton's first law of motion states,"Every body continues in its state of rest, or of uniform motion in a right line, unless it is compelled to change that state by forces impressed upon it." Again ...
0
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1answer
78 views

What happens if you ride a bike on to a moving sidewalk?

If a person were to riding a bicycle on normal ground then ride onto a conveyer moving in the forward direction of the bicycle (like a moving sidewalk in an airport), would the bike slow down or speed ...
1
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3answers
467 views

What is the origin of pseudo force in non-inertial frames? [duplicate]

When a bus stops suddenly, I can "feel" a force pushing me. This is exactly as if someone really pushed me. Same is the case while doing a turn in a car, I can "feel" a force pushing me away from the ...
3
votes
6answers
1k views

What is the force that pushes a car upwards when moving on a banked road?

On banked roads, if the road is frictionless, we can drive a car in circular motion only at a particular velocity called safe velocity. Now if the velocity is less than the safe velocity, then the car ...
2
votes
1answer
208 views

What would be the equations of motion in this case of initial & final rolling on a ball in an accelerating car

Suppose there is a car and a ball inside it can roll. Now the car accelerates with acceleration a. Now what would be the the equations of motion for the ball in the car from both the frames of the ...
3
votes
4answers
1k views

Relativistic electromagnetism and electromagnetic forces on 2 protons

The question I have about it is how we can get the same result of net force acting on the individual protons if we judge the system from 2 different reference frames. One using more of the magnetic ...
-3
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1answer
114 views

If an Object at Rest has zero net force, why does it have gravitational potential energy? [closed]

Also, if I throw an eraser on a table shouldn't it's g.p.e be $mg$ times its height from the ground, plus the additional height on the table instead of just the height on the table?
2
votes
3answers
181 views

Why Objects still move under the effect of fictitious force?

As I read in many books and websites, An inertial force is a force that resists a change in velocity of an object. It is equal to—and in the opposite direction of—an applied force. If the inertial ...
0
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3answers
74 views

Dependence of curved path on frame of reference and force

I was studying projectile motion and suddenly thought that is it possible for particle to move along a circular path without any force acting on it ? (I m not talking about circular motion as it ...
2
votes
1answer
137 views

Laws of dynamics and reference frame

I was having trouble understanding the following text given in my mechanics textbook:- If we choose an arbitrary set of frames of reference which are all in uniform rectilinear motion relative to ...
1
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2answers
112 views

The same event interpreted by different observers

While my physics teacher was explaining pseudo forces to us he gave the following example : An elevator is accelerating upwards. In it there is a bob strung up by a rope. There are two observers, A ...
0
votes
1answer
49 views

Some questions about forces

If I am sitting inside a closed sphere (I can't see the outside), can't I feel when the sphere is at constant speed ? Can I feel when it is accelerating ? Why ? The defination of force given ...
4
votes
2answers
1k views

Is Newton second law covariant or invariant?

Is Newton second law covariant or invariant between two inertial frames, moving with uniform traslational motion with respect to each other? If it is invariant then, indipendently from the frame, $\...
2
votes
2answers
500 views

Is polar coordinates frame non-inertial?

Consider the acceleration expressed in polar coordinates. $ \left( \ddot r - r\dot\varphi^2 \right) \hat{\mathbf r} + \left( r\ddot\varphi + 2\dot r \dot\varphi \right) \hat{\boldsymbol{\varphi}} \...
1
vote
1answer
53 views

In rotating frames, particles do not travel at constant velocity?

If we measure a particle's trajectory in a rotating frame of reference as $\vec x=\vec x(t)$, then $\frac{d^2\vec x}{dt^2}=0$ could be zero? I'm trying to explain why the Newton's first law of ...
0
votes
2answers
394 views

Inertial forces and centre of mass

Is inertial force always attached to the centre of mass of the object? Why? What rules cause this to happen? See the example below of the leaned bike in a corner. The force $m\frac{v^2}{r}$ pointing ...
1
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2answers
4k views

Distinguishing real forces and fictitious/pseudo forces in Newtonian mechanics

In understanding the law of inertia I had to consider the motion of bodies screened from the so called "real forces". What characterises these real forces? What makes us call them real? Or what is ...
-1
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1answer
80 views

How to prove that “all unaccelerated frames behave likely for all isolated bodies”? [closed]

Say in an unaccelerated frame "S" a "isolated body A" moves with constancy of velocity , can we predict mathematically that any other such body B will move with same velocity in that frame.... My ...
-1
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2answers
16k views

Can a pilot in a small spaceship feel G force in space?

I am not really good in physics so I might be wrong at some points, but here is the situation. Consider a spaceship of the size of a fighter plane. And like a fighter plane, the ship is very mobile. ...
0
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1answer
31 views

Who is moving and with who's relation?

What if we are in a cube of 3×3 m  which is further enclosed in a sphere of radius 50 m? And the sphere start to rotate on its own axis would we experience force? If not then what happens if there is ...
2
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2answers
1k views

Who plays the role of centrifugal force in an inertial frame of reference?

It is noteworthy to quote a sentence from my book, It is a misconception among the beginners that centrifugal force acts on a particle in order to make the particle go on a circle. Centrifugal ...
1
vote
1answer
200 views

Fictitious forces and $\omega$

I have been studying fictitious forces, such as the centrifugal force and Coriolis force. The equation for the centrifugal force is given by: $$F_{centrifugal}=-m\omega\times(\omega\times r)$$ My ...
-1
votes
1answer
729 views

Don't Inertial forces obey Newton's third law? [duplicate]

I read in a book (Fundamentals of Mechanics by IE Irodov) that inertial forces do not obey newton's third law. I am unable to imagine and get this in my mind. It states: "Inertial forces are not ...
8
votes
4answers
2k views

Why does Newton's third law exist even in non-inertial reference frames?

While reviewing Newton's laws of motion I came across the statement which says Newton's laws exist only in inertial reference frames except the third one. Why is it like that?
4
votes
2answers
7k views

Fictitious forces confusion

I have a hard time understanding the subject of fictitious forces. Let's discuss a few examples: 1) I'm sitting inside a vehicle which is accelerating in a straight line. I feel like someone is ...
1
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2answers
361 views

Fictitious Forces $\overset{?}{⇔}$ Constraint Forces (re: D'Alembert's Principle)

Are fictitious forces and constraint forces the same thing?