This tag is for the classical concept of forces, i.e. the quantities causing an acceleration of a body. It expands to the strong/electroweak force only insofar as they act comparable to ‘classical’ forces. Use [tag:particle-physics] for decay channels due to forces and [tag:newtonian-mechanics] or ...

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2
votes
1answer
40 views

Am i trying to fly by pulling myself up by my hair?

I'm currently trying to build a multi-rotor of my own, and am testing it when i noticed that the lift that i am supposed to be getting is wayy less than what i am expecting. I have a rectangular body ...
-1
votes
4answers
70 views

Can a component of vector be greater than the vector itself?

...we have at our disposal an infinite variety of ways of resolving a given force into components. . . . The fact that any component may happen to be larger than the vector itself doesn't ...
0
votes
2answers
28 views

Calculating the flex of a solid bar under force

I want to calculate how much a solid bar will flex when force is applied to it. The set up looks like this: The rod (in green) rests on two stationary points, and the force is applied in the center ...
2
votes
1answer
186 views

Is force the derivative of energy?

In my lecture today my professor briefly mentioned that force is the derivative of energy but I did not really get what he meant by that. I tried to express it mathematically: ...
0
votes
0answers
15 views

Rotational stiffness of a rod with attached spinning mass

I have a larger, more complex situation with various forces and perturbations etc., but I'm stuck on what I expected to be a simple situation. Given a mass (lets make it spherical for ease) rotating ...
0
votes
1answer
30 views

Very confused about effective spring constant

I know that for springs in parallel, the effective spring constant is $k_1+k_2$ and for springs in series the constant is $1/(1/k_1+1/k_2)$. But there are some weird problems where finding the ...
3
votes
1answer
45 views

Springs at an angle [on hold]

I'm trying to find the equation of motion for the following system: This is how I proceeded: Let's call the length of the hypotenuse $s$. Then, $$F = 2 \sin{\theta}\cdot-k(s - l_o) = -2kx ...
1
vote
1answer
17 views

A particle collides with another particle in an (infinitesimally long?) elastic collision, what is the resultant force?

When an object collides with another object in an elastic collision, the first object exerts a force on the second object (and vice versa); how do you calculate the force that the object experiences? ...
0
votes
0answers
22 views

Finding the effective force constant in an accelerating frame [on hold]

Consider problem #16 here: http://www.aapt.org/physicsteam/2013/upload/exam1-2012-unlocked-solutions.pdf Let me share my thoughts, and hopefully someone can tell me where I am going wrong. ...
-1
votes
0answers
20 views

2012 F=MA Contest #12 on tension [on hold]

There is an interesting problem (#12) from the F=MA contest: My approach: Let the tension in the string supporting the hanging weight be $T$. Since the angles between all the strings are constant, ...
-1
votes
0answers
16 views

What is the acceleration of the multi-mass system? [on hold]

Three blocks are held up by a force of 65 N. The top mass is 5 kg and middle mass is 3 kg and the bottom mass is 2 kg. What is the acceleration of the system?
2
votes
1answer
38 views

How much weight would I need to put on the end of a tube to break it?

Say I have a tube with a circular cross-section made from some material (for an example, I'd like to use acrylic). I support it horizontally from one end and hang a weight from the other end. How ...
6
votes
3answers
737 views

Why don't we consider jerk in physics classes? [duplicate]

When i got more into physics, i started asking myself if just like acceleration represents the growth of speed, something else could also represent the growth of acceleration itself. And it came that ...
0
votes
1answer
32 views

Force between two point dipoles

What would the force between two parallel point dipoles be? I was thinking of doing it the way force between two point charges is found out, by finding the field and then the force but I am not able ...
0
votes
0answers
55 views

Why golf balls travel faster if they spin?

From the book I have been given to read I found that balls spin due to the centripetal force but i am confused about how exactly do the resultant force causes it to spin and move forward about the ...
-2
votes
0answers
39 views

Force Required to Move an Object at the Speed of Light [on hold]

I am currently struggling on a problem that asks What magnitude of force is required to accelerate a $2~\text{kg}$ car to $1.00~\text{m/s^2}$ given its initial velocity is $90\%$ the speed of ...
0
votes
0answers
24 views

how can I use the Pythagoras theorem in the case of a block with mass on incline? [on hold]

How can I calculate the acceleration of an object on an incline by using Pythagorean's Theorem? I'm confused between using Pythagoras' theorem or vectorial calculus to find acceleration. For ...
0
votes
4answers
45 views

Find the work done in moving an object along a vector r with a force F [on hold]

$$r=3i+5j-2k$$ $$F=3i-3j+2k$$ What do I do. I know that work = force x distance. However, what vector operation should I do? I was wondering whether I should possible find the unit vector of r and ...
0
votes
1answer
29 views

Newton's 2nd and 3rd Law clarification [duplicate]

Hi I have a quick question. I know this may be a common question. If N3L states that there's an equal and opposite force, why do things still move? I have read up a lot and this is my understanding. ...
3
votes
6answers
958 views

Elevator cabin problem

The following passage is extracted from the book "Concepts of Physics, Part 1" by H C Verma: Let us consider the situation shown in figure. An elevator cabin falls down after the cable breaks. ...
3
votes
3answers
111 views

Why are forces independent from the frame of reference?

The following question occurred to me while reading a proof of the following statement: If K is an inertial frame of reference, then a K’ frame of reference, which is moving with a constant ...
0
votes
3answers
51 views

Newton's Second law of Rotation

In my book (Halliday Resnick Walker) there is a solved example which is as follows There is a uniform disk with mass $M$ = 2.5kg and radius $R$ = 20cm, mounted on a fixed horizontal axle. A block ...
0
votes
3answers
59 views

What force $\vec{F_{1}}$ is needed to balance the beam in the diagram below? [closed]

What force $\vec{F_{1}}$ is needed to balance the beam in the diagram below? I know that $\sum \vec{F}$ must equal zero. I also know that since the unknown force is farther from the pivot, ...
1
vote
1answer
35 views

Can gravitational force act as an impulsive force in any case? [closed]

Can gravitational force be termed as impulsive in any case? I' m thinking about it but couldn't get any answer. When two heavenly objects collide then the force exerted on each of them during the time ...
3
votes
3answers
1k views

How hard would I hit the ground on Mars?

How do you calculate with how much force a mass would hit the ground when falling from a certain height? In particular, I'm curious to know how the force of impact on Earth compares with Mars, so ...
25
votes
3answers
3k views

Change my mind! Classical spring problem [on hold]

If the spring in Figure A is stretched a distance d, how far will the spring in Figure B stretch? The spring constants are the same. The answer is "by half". I don't get it, to me it's the same.
1
vote
2answers
45 views

What role does static friction force play for a rolling object? How can I know what direction it points?

Fundamentally, what does a friction force do for a rolling object? I am very confused by the way my textbook explains it. In my textbook , it says: A wheel rolling on a horizontal flat surface at a ...
0
votes
1answer
23 views

Find angular velocity of motor

I'm quite bad at this, but I'm trying to change that and I need some assistance. Please bare with me while I attempt to explain what I'm trying to figure out and correct me where I'm wrong. Basically ...
3
votes
3answers
581 views

Is the shell theorem only an approximation?

I've read the shell theorem during gravitation lectures, i.e. I know it states that the net gravitational field inside a 3D spherical shell or a uniform 2D ring is zero. Now, assume a thin spherical ...
1
vote
1answer
138 views

Is gravitation really a conservative force?

A spinning gyroscope has a rigidity in space. That means it maintains its axis in relation to space – and not to the surface of the earth: Imagine a spinning gyroscope that is freely mounted in ...
-2
votes
1answer
54 views

Tension on strings holding a weight [closed]

It's a 100% standard problem in any basic physics course, and I cannot solve it. Here's the scenario: What is the tension in the strings (T1 and T2)? My thoughts were (cos/sin rewritten as ...
1
vote
1answer
44 views

Does the outflowing water create a thrust on the bucket?

Let's consider the the bucket with water, which has a small hole at the bottom. Let the bucket lift up with a constant force $\vec F$. Water in the bucket, of course, flows out of it. Questions are ...
0
votes
0answers
27 views

Origin of the shape of the planets [duplicate]

Looking at our 8 planets over the years has left me a huge unanswered question. I know these planets compared to space is like a grain of sand on our entire planet. All the planets have the basic ...
0
votes
2answers
59 views

How does friction help the car to move forward? [duplicate]

Below is the extract from my book. There is a car with four wheel drive system and during acceleration, the engine causes the tires to push backward on the road surface. This push produces ...
1
vote
2answers
41 views

Stable equilibrium in a gravitational field with 2 masses [closed]

Suppose you have two point masses $M_1, M_2$ in space and you locate the point $A$ on the line between them such that an object placed at $A$ is in equilibrium (the only forces acting on the obect are ...
0
votes
1answer
44 views

Why we can omit some forces while applying linear momentum principle

While applying linear momentum principle, namely that if force is zero linear momentum of the system is constant, in textbook they don't count for $N$ force from $M \to m.$ This force have component ...
0
votes
2answers
26 views

Different sized pneumatic Pistons [closed]

If two different sized pneumatic pistons have the same amount of air pressure, will they exert the same amount of force? If not, would a bigger or smaller piston have more force? And an explanation ...
-1
votes
0answers
39 views

An old mechanical paradox [duplicate]

A rope (whose weight may be neglected) hangs over a smooth pulley; it has one end fastened to a weight of 10 stone, and the other end to a sailor of weight 10 stone, the sailor and the weight hanging ...
0
votes
1answer
32 views

What are the preferred height and diameter proportions for a rocket model?

I'm pretty sure, that if you make a rocket that's relatively small in height compared to diameter, it will most likely not fly very high and probably spin out of control. What about a rocket that is ...
1
vote
2answers
32 views

End current without touching wire

Say I am sending a pulse down a five foot wire. If I want the pulse to not reach the end of the wire, but instead reflect at say the two foot mark, how could I achieve this without physically ...
2
votes
1answer
79 views

Why doesn't a parachutist, according to Newton, “fall” upwards (because drag is larger than gravity)?

Part of the second law states that an object will accelerate in the direction of the unbalanced force. However, I've been thinking about parachuting and skydiving a bit lately, and I know that when ...
0
votes
2answers
49 views

When is tension constant in a rope?

Suppose we have a massless rope with pulling forces applied at each end. In which scenarios is the tension in the rope constant throughout? For example if there is a knot in the rope the tension is ...
0
votes
3answers
60 views

Force and direction of velocity

If the angle between force acting on a particle and velocity of particle is zero degree, the value of velocity will increase. If this angle is 180 degree, the value of velocity will decrease. If this ...
0
votes
1answer
35 views

Calculate a drag force on a sphere?

Objective Work out a drag force for a unit sphere traveling through air at velocity. Values for formulae are below. The context of this question is that I am calculating this in an atmospheric ...
2
votes
3answers
175 views

Is work done = change in KE, or change in mechanical energy?

Starting from $F = ma$ we get: $$ F=m\frac{dv}{dt} = m\frac{ds}{dt}\frac{dv}{ds} = mv\frac{dv}{ds} $$ which leads to the work done: $$ W = \int Fds = \int mvdv = m\frac{v^2}{2} - m\frac{u^2}{2} ...
0
votes
3answers
53 views

Centripetal and centrifugal force

If a stone is rotated with the help of a rope, then both centripetal force and centrifugal force will be liberated. The magnitude of that forces are same, but direction of them are opposite to each ...
3
votes
2answers
164 views

Why do we need torque separately from force?

I'm studying physics for a couple of month now and and I am currently finding it a bit unsatisfying how the basic physical concepts are presented, meaning often times we only get a formula ($\tau=r ...
1
vote
2answers
68 views

Can magnetic force do work? [duplicate]

I have been told numerous times that magnetic force do no work at all but I have some trouble digesting this fact. Now suppose we have two straight wire with some current, they certainly can feel ...
1
vote
2answers
89 views

Can other fundamental forces bend spacetime?

I was wondering what makes gravity so special that it bends spacetime? and if it is part of the four-fundamental forces, why or why cant the other forces bend the time space continuum?
0
votes
0answers
38 views

Intuition of centrifugal force [duplicate]

I heard that centrifugal force does not really exist; that it is made as opposite substance to centripetal force. Is it true? Could someone define for me what centrifugal force is in terms of vectors ...