Tagged Questions

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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0
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2answers
32 views

Force balancing - Newtonian mechanics

If a horse pulls the carriage, the carriage should pull the horse with equal force (Newton's third law), then how does the whole system move? I drew the free body diagram but not yet figured what ...
0
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0answers
27 views

Force-carrying particles instead of forces

Are there physical theories in which notions of particle are used without the concept of force? I know about gauge bosons, see: http://en.wikipedia.org/wiki/Force_carrier and ...
18
votes
6answers
2k views

Why are a motorcycle's front brakes more effective than back?

I've noticed that when I apply the front brakes on my bike it stops quite quickly. If I apply the back brakes at the same speed, it skids rather than stopping quickly. Why?
1
vote
1answer
83 views

Can there be force without motion?

I am confused. Can you have a force or tension without motion? Take for instance two robots with jet packs connected via a cord, each is flying in opposite directions. The tension of the cord is ...
0
votes
0answers
18 views

Forces at each point for a simple truss [on hold]

I have a truss here: It is given that the forces at point 2 are horizontally and vertically. Positive values for lowercase f forces indicate tension, and negative ones indicate compression. I ...
0
votes
1answer
15 views

Magnetic interaction of wire and rectangular loop

In this video, Prof. Lewin shows an infinitely long wire and a rectangular loop at a distance $r_1$ from each other, each carrying a current. He then calculates the magnetic field resulting from the ...
0
votes
1answer
35 views

Definition of torque for a continuous body

I am working on basic physics definitions. Given a particle at position $r$ (in some coorinate reference system) upon which acts a force $F$, the $torque$ $\tau$ is defined by \begin{equation} ...
0
votes
3answers
74 views

How much further can I throw a baseball (148 grams) than a grenade (453 grams)?

Question: Over a flat plane, how much further can I throw a Major League baseball than I can an M67 grenade? Major League baseball: 148 grams M67 frag grenade: 453 grams For a baseline of how ...
0
votes
4answers
33 views

How to find total force on an object?

If there are are a multitude of forces on an object, acting on it in different directions, how do you find the TOTAL force? I know you add up the x components and the y components individually, but ...
-2
votes
0answers
31 views

Finding the angle of fuzzy dice in a car when deccelerating [on hold]

You are driving at 25m/s when you see Bambi in the road! The coefficient of friction between your tires and the ground is .8. You slam on your brakes praying friction is great enough for Bambi to ...
0
votes
0answers
21 views

Tension - Force Question [on hold]

A 72kg sled is pulled forward from rest by a snowmobile and accelerates at 2.0m/s^2 for 5.0s. The force of friction acting on the sled is 120N [backwards]. The total mass of snowmobile and driver is ...
-5
votes
0answers
25 views

Two blocks on a pulley [on hold]

A block of mass $m_1 = 41.3 \,\rm kg$ on a horizontal surface is connected to a mass $m_2 = 13.2\,\rm kg$ that hangs vertically as shown in the figure below. The two blocks are connected by a string ...
0
votes
3answers
72 views

In this pulley system, if the mass was on the table greater than the handing mass, would tension equal Fg of the hanging mass? [on hold]

If the mass on the table was greater than the hanging mass, would the the tension force equal the force of gravity on the hanging mass?
4
votes
2answers
56 views

Reaction force for buoyancy?

According to Newton's 3rd law each force (action) has a counter-force (reaction). What is the reaction (counter-force) of buoyancy?
1
vote
1answer
32 views

Net Force on Individual Masses, or the entire system? [on hold]

In the picture, would the net force on each individual mass take into account both masses or just the individual mass? For example, would the net force on the first mass be equal to $am_1 = ...
-10
votes
0answers
74 views

Deriving Newton's Second Law [on hold]

How do I derive μ = Tan[θ] ? Step by step instructions please.
2
votes
1answer
35 views

Increase in kinetic energy as some one walks to the centre of a merry-go-round?

When someone walks to the directly centre of a merry-go-round the total kinetic energy of the merry-go-round and person system increases. (assuming the kinetic energy due to the person walking to the ...
-1
votes
1answer
21 views

Can the nonlinear hydrodynamic forces be neglected when a capsized ship is righting? [duplicate]

Can the nonlinear hydrodynamic forces be neglected when a capsized ship is righting? Thank you for answering my question.
1
vote
3answers
343 views

Is Newton's third law universal, does it apply to momentum or also to forces?

I read all the previous answers concerning the 3rd law and I have seen that it is definitely not universal, (Edit: but conservation of momentum is. If it is not universal it should be not a problem to ...
4
votes
2answers
493 views

Does a force act on the body during collision

Consider two bodies A(black) and B(red) having equal mass. A is moving at a constant speed towards B, which is stationary. At certain point of time, they collide elastically, $\therefore u_{A}=v_{B}$ ...
2
votes
2answers
54 views

Can we harvest energy from constant gripping?

Gripping things hard needs energy even though nothing really moves. So I think we could harvest energy from this action, but I know that any type of energy harvesting requires moving parts. So can ...
2
votes
1answer
45 views

Confused about gravitational potential energy [duplicate]

So learning the concept of gravitational potential energy, my professor says that when lifting an object without any acceleration, the force we exert on the object to lift it is the same as the force ...
0
votes
0answers
29 views

How to calculate how much air is leaking out of an object?

I have a pressurated pvc pipe. I am wondering how long it would take for it to leak out on a small tube. I really just want to know how to do the equation, so I could figure it out depending on the ...
0
votes
0answers
13 views

Addition of forces in dielectric material

In this paper (page 2 of document) it is said that: Because this calculated force was comparable to the gravitational force, they assumed that the same would be true for the forces on a ...
0
votes
0answers
18 views

A box up an inclined ramp with a coefficient of friction [closed]

A 6.25 horsepower motor to pull the boxes a distance of 8.35 meters up a ramp inclined at an angle of 36.2º with respect to horizontal. The boxes have a coefficient of kinetic friction of 0.381 as ...
0
votes
0answers
10 views

What is the force of the wind resistance? [closed]

A sled of mass 15.0 kg is pulled forward with a force of 35 N. Also a frictional force of 12.2 N acts on the sled. Finally a wind resistance acts on the sled. Over a period of 18.0 s the sled ...
3
votes
1answer
37 views

Fruit flies in a bell jar [duplicate]

You place a bell jar on a scale and the scale registers x grams. You then trap y grams of flying, non-landing fruit-flies in the bell jar. What does the scale register? x grams? x+y grams? Something ...
1
vote
1answer
41 views

Hooks Law and acceleration [closed]

A 435 gram sharpened piece of iron rebar into a spring loaded device. It takes a force of 355 Newtons to compress the spring by 27.5 cm. With what speed does the rebar shoot out of the device? ...
1
vote
2answers
48 views

For a massless pulley moving upwards with acceleration, is the upward force equal to the downward force?

Imagine a massless and frictionless pulley with two weights hanging either side of the pulley by a massless string. Like this except not attached to a ceiling Rather than being fixed to a ceiling, ...
4
votes
6answers
108 views

What is the relationship between force and momentum in collisions?

I know that $ \Sigma F = \Delta mv/\Delta t$. But if we had a marble that moves in a straight line at a constant velocity and colloids with another marble. Because of the law of conservation of ...
1
vote
1answer
41 views

Why does gravity enact force? [closed]

Gravity would cause two objects in a vacuum to move toward each other. I understand that gravity is a force that exists as a product of energy's original conversion into mass and the continuing change ...
5
votes
3answers
135 views

Gravity - Force or Result?

I am no Physicist, but I enjoy reading about Physics. However reading about leading theories such as M-Theory and others they speculate about the existence of the Graviton. In my past reading of ...
2
votes
2answers
57 views

Deriving the Coulomb force equation from the idea of photon exchange?

Since Newton's law of gravitation can be gotten out of Einstein's field equatons as an approximation, I was wondering whether the same applies for the electromagnetic force being the exchange of ...
-2
votes
1answer
30 views

Coulombs Law step by step help

How do you calculate the the magnitude of the total force of three charges and also the angle it makes with the x-axis? Knowing the magnitude and also the 2d co ordinates of the charges. I have ...
2
votes
4answers
137 views

Kinetic energy vs. momentum?

As simple as this question might seem, I failed to intuitively answer it. Let's assume there is a $10,000$ $kg$ truck moving at $1$ $m/s$, so its momentum and KE are: $p=10,000$ $kg.m/s$ and ...
1
vote
5answers
198 views

A force is exerted on a body, kinetic energy increases but no work is done by the force. Why?

After reading the article, I was totally perplexed . I was reading the External forces and internal energy transfers in Principles of Physics by Resnick,Halliday,Walker. It goes like that An ...
0
votes
1answer
22 views

Forces Create Angular Acceleration And “Straight” Acceleration - But How Much Of Each?

Let me set up the following problem for a rectangle floating in space: We know its dimensions. We know its mass. There's a force pushing it for a known amount of time - we know the angle & ...
0
votes
1answer
20 views

With what speed must e.g. a car drive into a turn so it won't drift out? [closed]

I am trying to figure out the following question: with what speed must e.g. a car drive into a turn so it won't drift out (if a turn is a circumference of a semicircle)? e.g. $r= 5 m$ $a_r= ...
0
votes
0answers
31 views

Collision force calculation with no future knowledge

For a personal project, I am attempting to write a fairly realistic collision simulator (for relatively large objects, not quantum stuff). As I was consulting my physics textbook and various online ...
0
votes
6answers
307 views

Why is kinetic energy stored as potential energy in a body during its motion against gravity?

Everyone knows kinetic energy is converted to potential energy in the body when it moves up against the earth's opposing gravitational force. But I am facing some problem with this. What I learnt ...
1
vote
2answers
40 views

Effect of movements of astronauts on International Space Station

I know that astronauts move in and around in ISS. When they move they also touch the modules of ISS and sometimes they apply force on the module to move. When this happens, as far as I know it affects ...
0
votes
1answer
21 views

Final velocity of a spring [closed]

I need to calculate the velocity of an object when it is thrown by a spring; we have to calculate the velocity from $U=\frac 12 kx^2$. Now I know that $U=L=F\cdot S$ and $S=\frac{v_f^2-v_0^2}{2a}$. ...
2
votes
1answer
107 views

How did Newton establish his famous third law of motion?

For every action,there is equal and opposite reaction . This is the famous Newton's third law of motion. But how did he come to this conclusion? We can prove 2nd law using calculus. But how did Newton ...
1
vote
1answer
42 views

Rotating metal sphere

My knowledge of physics is not that great, but I am always willing to learn. I have the following question: If we have a sphere made out of metal with a radius of 1 meter, and it rotates in an ...
4
votes
3answers
227 views

Why is it mandatory to lose energy to an opposing force?

A body must do work against an opposing force to continue motion. I have found this statement many times. But what is the reason behind it? Suppose $F_1$ is acting on a body to accelerate it (to ...
1
vote
1answer
36 views

Is there an equilibrium for water and air in a tank?

I'll try my best to explain my question with examples because I don't have much knowledge on the theory. So say that I had a block of water in air, a cube of water, that is dropping. If the cube ...
2
votes
1answer
47 views

Just for confirmation: About conservative forces [closed]

Once I posted in the following thread and wondered, how I could picture/understand conservative forces best. I think, that I understood my problem now and everything became clearer. So just for ...
1
vote
2answers
56 views

Why is force a localized vector and not a free vector?

A vector which is drawn parallel to a given vector through a specified point unlike free vector in space is called a localised vector. The effect of a force acting on a body depends not only on the ...
4
votes
1answer
35 views

Physics behind the “Switch Pitch”?

I've come across this toy called a "Switch Pitch" designed by Chuck Hoberman. It's a ball that when tossed into the air (with some amount of rotation), inverts and changes colour. Made of plastic, ...
9
votes
1answer
1k views

Would you die before reaching the ground?

If you were to jump off a tall building, let's say Burj Khalifa, is it true that the pressure difference would be so strong as to kill you before reaching the ground?