Questions tagged [forces]

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 the [particle-physics] tag for decay channels due to forces and [newtonian-mechanics] or one of the other subtopics of [classical-mechanics] for the dynamics of classical systems.

Filter by
Sorted by
Tagged with
0
votes
5answers
104 views

Newtons Third law - does it apply regardless of size difference between interacting bodies?

This is a theoretical question. Assume I have a $1000 \;\text{kg}$ box and just 1 molecule (say Oxygen) in a 100-meter-tall hollow vertical cylinder. The cylinder walls are much wider than the box ...
2
votes
5answers
64 views

Example on impulse

A rubber ball of mass $50g$ falls from a height of $1m$ and rebounds to a height of $0.5m$. Find the impulse and the average force between the ball and the ground if the time for which they are in ...
0
votes
2answers
46 views

Tension force and Newton's third law

When a horse pulls a cart, suppose connected by a string, it produces a tension $T$ in the string. The cart in turn pulls the horse by an equal force $T$ in the opposite direction. If this T>f, the ...
2
votes
2answers
106 views

Help me in understanding use of vector in this problem

In the question here, velocity of block A is $5 \;\text{m/s}$. To find the velocity $v$ of block B, why do we use $v \cos 53° = 5$ instead of $5 \cos 53° = v$. Isn't the $5 \;\text{m/s}$ velocity ...
2
votes
1answer
44 views

How can the $x$-components of the frictional force and the normal force be the same for a static block on an incline? [closed]

I recently was assigned this problem as part of my homework: "A block sits on a plane that is inclined at an angle $\theta$. Assume that the friction force is large enough to keep the block at ...
7
votes
3answers
214 views

Can static friction force alone make the center of mass accelerate in this example?

I came up with an idea of motion of ceter of mass the day before yesterday but couldn't find any solid answer for the cause of its motion. Take the example of a man (say of mass $50$$kg$) and a tank (...
-3
votes
3answers
57 views

Consider the following figure. A man sits in a pan and tries to raise himself by pullingthe rope downwards [duplicate]

Consider the following figure. A man sits in a pan and tries to raise himself by pulling the rope downwards. Will he be able to raise himself up? Explain. I understand that it is not possible as like ...
0
votes
0answers
27 views

Could the ITER central solenoid lift an aircraft carrier 2 m into the air?

This claim is made in many places around the internet, presumably repeated from an ITER press release. But are there caveats? Does the aircraft carrier need to be in water (so only the no-longer-...
0
votes
1answer
45 views

Why work done by tension (like string force) is always zero?

A fixed disc free to rotate about its center (a flywheel) has a string wrapped around it, with a block attached to it. As the block falls, The tension in the string makes the disc rotate. Now, when ...
0
votes
3answers
59 views

What is the pressure that dark energy exerts on stars and planets while increasing the distance between them?

What is the pressure that dark energy exerts on stars and planets while increasing the distance between them? I can understand that the pressure should be at a volume scales lower than molecules ...
0
votes
0answers
31 views

Morison Equation - Value of $k$ not working

Need a hand with the Morison Equation with $k$ giving me a headache. I'm following a video online trying to calculate the force on a structure I am designing for work. I try to follow videos using ...
2
votes
1answer
58 views

Potential energy and force [duplicate]

Why force is negative gradient of potential energy? Why negative sign is involved in this definition?
1
vote
3answers
73 views

Example that seems to violate conservation of angular momentum [duplicate]

Mass m is rotating on a horizontal friction-less plane around a tiny hole. A massless string is connected to mass m and the other end of it is slowly pulled. Taking the center as our origin we see ...
0
votes
1answer
40 views

Formula for calculating sliding friction

What is the formula for calculating frictional force of a sliding body? I have already tried $F=UR$ but it is not working.
0
votes
3answers
40 views

Action-reaction force diagrams

I have an issue with the force diagram examples of reaction forces. It doesn't define where the "action"/applied force is coming from. If we were to draw free body diagrams, then for object ...
2
votes
2answers
41 views

Why do I feel centrifugal force If I move with constant speed on a turn?

Title sums it up pretty much, I'm studying for my physics exam right now and I just can't wrap my head around this
1
vote
6answers
175 views

Why $F=ma$? Why not $F=mvs$ or something else? [closed]

Newton defined rate of transfer of momentum from one particle to another as force. Can we predict motion using F=mvs or something similiar instead of $F=ma$?
17
votes
2answers
932 views

Since photons are said to be the force carrier of electromagnetic force, does it mean that photons get transferred from golf club to golf ball?

Just like it says in the question title. I have heard that photons are force carriers of electromagnetism. Is it not true, that when a golf club imparts force on to a golf ball, then the fundamental ...
0
votes
3answers
66 views

Problem with Action-Reaction pairs and gravity [duplicate]

There are lot of question on this site similar to this, but they give contradicting opinions. When standing on earth, my gravitational pull to the earth and earth's gravitational pull towards me ...
-1
votes
3answers
92 views

Is EMF a force? [duplicate]

I had a confusion. EMF stands for electromotive force. Is it a force? I have a short question and I can't elaborate more but this site is not allowing me to post so I am writing.
1
vote
1answer
45 views

Friction problem when object is constrained

A $60 \;\text{N}$ force is acting on an object of mass $10 \;\text{kg}$ which is placed against a wall touching it. What is the normal force $N$ applied by the wall? My method: Since the object ...
2
votes
3answers
178 views

Problem with gravity

Sorry if this question is dumb, but I don't seem to have a grasp on it. Suppose you are on a rock in space, with no external forces acting. The rock attracts you with a force given by $$F=G\frac{...
1
vote
3answers
75 views

Is pseudo force just an ad hoc number to explain motion in non-inertial frames?

Consider an observer in a non-inertial frame $S$ who observes a particle's motion with a relative acceleration $\vec a_s$ and further calculates (or was told by his fellow observer in an inertial ...
0
votes
2answers
119 views

Time taken for a body to crash into the sun [closed]

A small body starts from rest towards the Sun from the position of Earth, find the total time it takes for the body to crash into the Sun (assume Sun is a point object and no other forces act on the ...
7
votes
4answers
866 views

Parallelogram law of vectors

[This is a very silly question. Will be a great help if someone could answer this question] How is this law proven? I am not asking about the proof itself rather asking about the preliminary ...
0
votes
5answers
123 views

Why do we multiply $\cos θ$ in the formula for work?

I know that the formula for work, $W = FS\cos\theta$, where $F$ is the applied force, $S$ is the displacement of the object and $\theta$ is the angle between the applied force and the displacement of ...
0
votes
2answers
58 views

Will the position of the Centre of Mass remain unchanged?

I know that internal forces won't accelerate the centre of mass of system, but assuming there are three objects in a system and two of them move due to the internal force exerted by one and the ...
0
votes
1answer
70 views

Tension at any point of a hanging rope

A common question to those initial practitioners of classical mechanics it to find the tension of a rope hanging between two trees, at the end and the middle. Below a graphical description of the ...
0
votes
1answer
45 views

Understanding the balance of forces

An "object" that has the shape of an inclined plane has a slot that carries a roller bearing attached to an extension spring. When a force F1 is applied to the left, the object moves and the ...
1
vote
5answers
70 views

Please explain the walking mechanism

When a person walks, he exerts a force on the road, lets say $F$, and the road exerts a force on the legs (friction), lets say $f$. Newton's third law says that $F = f$, so why is $f - F = ma$? Where ...
-1
votes
1answer
60 views

What are the forces acting on the block?

Imagine holding a piece of block with two fingers. The forces acting on it are $mg$ downwards, contact force $F$, and frictional force $f$. The block is at equilibrium under the action of this forces....
6
votes
5answers
259 views

'Simple' capacitor problem

I posted this question because I have a problem in grasping the connection between force on a charge and voltage potential equilibrium. So the problem is the following: we have a charged capacitor ...
0
votes
1answer
53 views

Confusion with force and time

It is said that force is an interaction that causes an object to accelerate. It is measured in newtons. $1$ N of force causes an object with a mass of $1$ kg to accelerate at $1$ m/s². Now let's ...
0
votes
0answers
43 views

How high can sand pile up?

I read a question about sand. In one answer, an hourglass was mentioned. Suppose you have enough fine, dry sand. If you create a pile of sand by letting a beam of sand fall down on the land (like in ...
0
votes
3answers
76 views

Conceptual doubts about Force and Gravity [closed]

First Question: Force applied for a span of time. Let's say a force $F$ is applied on an object of mass $M$. So, the acceleration of that object in the direction of $F$, would be, $a = F/M$. Now, if ...
1
vote
0answers
26 views

How to determine the force exerted by a fluid stream on a plate [closed]

This is related to Problem 1 in Chapter 2 of "Rocket Propulsion Elements, 9th Edition": A jet of fluid hits a stationary flat plate in the manner shown. (a) If there is 50 kg of fluid ...
0
votes
3answers
69 views

The unit of Torque [duplicate]

Whenever we define a physical quantity, we know what 1 unit of that quantity tells us. For example, when we say 5 Pa, we're saying 5 N force acts perpendicularly on every unit area of the material but ...
4
votes
1answer
78 views

Stair machine Vs stairs. which is harder?

I had a big argument at the pub about the stair machine being easier than actual stairs, and all the people there disagreed, saying that the only difference is air resistance? Are they kidding? My ...
0
votes
1answer
29 views

A runner against the wind

We have a runner that is running against the wind. The wind speed is $10 m/s$. The runner is using the same power when he is running against the wind and also when there is no wind, but we know, that ...
0
votes
2answers
36 views

Is the value of the work done by the forces acting on a rigid body frame dependent?

I was going through the definition of "Work of Forces Acting on a Rigid Body" in Wikipedia . Here they have mentioned that work done can be calculated by taking any reference point on the ...
0
votes
1answer
34 views

External force and centre of mass [closed]

I’ve read that linear momentum of a system will be constant when there is no external force on the system. Thus, the velocity of the centre of mass will be the same. Thus, this means that the position ...
3
votes
0answers
52 views

Struggling to prove Newton's Law of Gravitation starting from smaller bodies

I have seen at least four different posts in this website in which the OP asks for a proof of Newton's Law of Gravitation (often without stating from which axioms the proof should start) all of which ...
0
votes
1answer
57 views

Force between two charged shell [duplicate]

Suppose we have two charged shells with a distance between the two centers that they cannot be considered as point-like charges in the mutual interaction, for example three times the radius. Can we ...
0
votes
1answer
25 views

Impulsive forces

A force $F$ acting from time $t_1$ to $t_2$ on an object causes a change in its momentum $p$, as in $$\int_{t_1}^{t_2}Fdt=p(t_2)-p(t_1)$$ If this expression is now differentiated with respect to time, ...
0
votes
1answer
87 views

Why do ants feel more difficult to climb when height increases? [closed]

I have noticed that whenever an ant (carrying something) climbs a vertical wall, it easily climbs the lower part of the wall but as the height increases, the ant finds it difficult to climb and at ...
1
vote
1answer
42 views

The behaviour of acceleration of a ball in motion

I have a few doubts on how the acceleration of a ball works when we throw it up in the air, In my mind, I could imagine it in some different "real world" cases, So I am listing them all down,...
0
votes
4answers
49 views

Law of conservation of momentum and force

It is said that internal forces do not change the state of rest to motion only external forces can change it. But in case of a gun, a gun applies force internally to the bullet inside it and the ...
0
votes
0answers
18 views

Absorption chillers: can they achieve temperatures below zero Celsius?

If I understand correctly (history shows I probably don't), then the only reason why the absorption chiller evaporators are restricted (I hope that's the right word) to extract just enough heat so the ...
0
votes
3answers
46 views

Why is the normal force and the tension force greater than the weight in these examples? [closed]

A pendulum is suspended form the roof of an accelerating train. If it stays in equilibrium with respect to the train then an observer at rest will find the bob accelerating with the train. He will ...
0
votes
1answer
49 views

The projection of the Newton law for a ball moving in an italic direction

if I want to push the bowling ball in a direction which is not parallel to the lane, then I need to make a Projection on the axes (the x axis is parallel with the width of the lane and the y axis is ...