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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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 ...
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3answers
76 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, ...
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1answer
47 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
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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 ...
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4answers
3k views

Stretch length of horizontal and vertical springs

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.
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2answers
258 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 ...
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1answer
60 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 ...
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3answers
604 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 ...
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1answer
148 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 ...
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1answer
74 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
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1answer
52 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 ...
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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 ...
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2answers
155 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 ...
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2answers
60 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 ...
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1answer
47 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
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2answers
44 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 ...
0
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1answer
45 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
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2answers
42 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
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1answer
84 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 ...
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2answers
141 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 ...
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3answers
83 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 ...
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1answer
52 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
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3answers
202 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} ...
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3answers
85 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
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2answers
218 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 ...
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2answers
76 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 ...
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2answers
102 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?
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0answers
42 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 ...
0
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2answers
80 views

Boy , Table and the Newton [duplicate]

Suppose a boy is trying to stand on a table. If the table can hold upto a particular force, the boy would fall on to earth. If he stands on the table and providing greater force than the table can ...
0
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2answers
85 views

When a force pushes an object does the force move the object?

When a force pushes an object from a point $a$ to a point $b$ does this mean that necessary the force moves the object?
2
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1answer
110 views

Resemblance between Coriolis force and magnetic part of Lorentz force

If we interchange velocity with charge and omega that is rotation of a system with $B$, magnetic field, we get the same thing. Is there any deeper meaning to this same mathematical form?
2
votes
1answer
149 views

Conservation Of Angular Momentum of a falling stone

I am currently stuck on the following question. A stone is dropped from a stationary helicopter 500m above the ground, at the equator. How far from the point vertically below the helicopter does it ...
0
votes
1answer
81 views

3 pulley and 2 masses,relation between their accelerations [closed]

I want to find acceleration of each mass in this system. lets take length of rope between three pulleys as $L$. then we can use this relations ...
0
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1answer
32 views

A conceptual understanding of kg*m/s/s

Force is measured in kgm/s/s, or rather the rate in change of the rate in change of mass times length. Conceptually, what might the product of mass and length be? If force is the second derivative of ...
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2answers
333 views

When objects fall along geodesic paths of curved space-time, why is there no force acting on them?

On cseligman.com, it is written that So, we see things falling with an acceleration which we call the acceleration of gravity,and thinking that we live in a straight line , uniformly moving or ...
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2answers
155 views

Do objects really move in the direction of the force applied?

According to the second law of motion: Direction of the force is in the direction of change in momentum. Now, I came before a problem. Though an easy one, I was perplexed at a point. A ...
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0answers
50 views

Can someone please explain the forces acting on the rod? [closed]

Can someone please explain the forces acting on the rod.
5
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5answers
232 views

The elusive difference between force and impulse

Impulse is defined as the product of a force $F$ acting for a (short) time $t$, $J = F*t$, and that is very clear. What I find difficult to understand is how a force can exist that doesn't act for a ...
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0answers
39 views

Inclined pulley. Finding the $\frac{M_1}{M_2}$ [closed]

Problem As you can see in the picture, $M_1$ and $M_2$ are attached by a massless rope over a pulley. the height difference of $M_1$ and $M_2$ is $h$. The masses start to move and after $τ$ seconds, ...
32
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2answers
2k views

Why is the equation for friction so simple?

The general equation for the force of friction (static or kinetic) is $F_f = \mu * F_N$, where $F_f$ is the force of friction and $\mu$ is the coefficient of friction (its value is dependent upon the ...
0
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1answer
72 views

Action and Reaction - Time lag

Is there a time lag between action and reaction ? If there isn't such a time lag, the reaction force must cancel the applying force although they act on different bodies. My second question is that, ...
1
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2answers
61 views

Do components of force have direction when doing work?

When we get angle > 0, the x-component of force is along the direction of displacement and so their product is called Work. So the x-component of force is said to have direction of the respective ...
1
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1answer
38 views

How do you work out the energy requirement for a submerged pump?

I was wondering if you were to place a pump in a submerged container and then were to open a hatch allowing water to flood the previously vacant cavity how much energy would be required to discharge ...
4
votes
1answer
76 views

Are fundamental forces always attractive/repulsive, i.e. parallel to the separation?

If magnetic monopoles existed it would not be the case - the forces on an electron and a magnetic monopole passing by each other would be at right angles to the vector connecting the two particles! ...
0
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1answer
110 views

Ball flying towards me - Newton's third law is violated?

I was trying to answer the question of the flying ball here on the basis of Newtons third law and Momentum conservation. Here is what I have tried. Lets take $m_1$ (the ball) hits $m_2$ (the man). ...
2
votes
2answers
73 views

How to actually account for air resistance?

What's interested me in my studies thus far is that in a lot of beginner undergrad mathematics and physics courses we're often told to calculate trajectories, velocities, etc. by "ignoring air ...
1
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2answers
152 views

Inclined pulley with unknown hanging mass: when won't the system accelerate?

We have an inclined pulley with angle of $30° $ a block with mass of $10 kg$ placed upon it and It is attached by a rope over a pulley to a mass of $M_A$ which hangs vertically. If $μ_s=0.4$ and ...
1
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2answers
132 views

Force of a Train

Imagine that there are two trains and the first train is twice as long as the second train. They have the same mass per unit length and they are traveling at exactly the same speed. If the first ...
1
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1answer
67 views

How do you find the tension in the real world? (Given a rope in a pulley system)

I'm well aware of the formula to calculate tension, however, given a real world situation where you have a closed pulley system. How do you measure the force (i.e., tension) required to pull on the ...
0
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1answer
56 views

Problem of uncoupling a train

As a kid I have seen several movies, cartoon etc. in which usually one guy just uncouple (unplugs (?), dunno) the rest of a running train and then runs off with the locomotive at full speed and ...