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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166 views

Find the bending moment of a pole attached to a moving block

I'm having trouble with the following problem. What I've done so far: x-y is the usual coordinate system. $a=\frac{F}{m}=\frac{800}{60}$ and the y component of this is $a_y=a\sin{60^\circ}$. To ...
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1answer
88 views

Work done by complex field on complex plane

A force field is given by $F = 3z+5$. Find the work done in moving an object in this force field along the parabola $z = t^2 + it$ from $z = 0$ to $z = 4+2i$. I don't understand why conjugate ...
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2answers
244 views

Can there be energy with no force or energy with no power?

I think that both force (number of newtons) and power (p=ui(?)) implies that there is energy so we can't have force without energy and we can't have power without energy(?) But can there be energy ...
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1answer
151 views

Potential energy and average force? [closed]

A body of mass $15\,kg$ originally at rest $5\,m$ above the ground falls and penetrates $15\,cm$ into soft earth. Determine the loss of potential energy Determine the average resistance of the ...
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1answer
325 views

Hooke's law, springs

A spring AB with constant k is hooked in the end A to the ceiling. At the end B of the undefomed spring is hooked a mass of weight 100N. At $t=0$ the mass is let free with no initial velocity. Not ...
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2answers
780 views

What is the force of friction between two bodies given their masses and a force pulling them as a unit accross a surface?

Where a force of 200N pulls two blocks together(as one system) across a horizontal table top(µ=0.800) $m_A$ = 5.00kg, $m_B$ = 10.0kg Find the acceleration of the system. Find f$_k$ between B and A ...
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1answer
2k views

How to calculate the supporting force for a cantilever beam? [closed]

How do I find the supporting force $R_A$ and the moment $M_A$? Should I use the sum of moments or?
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2answers
341 views

Calculating restorative force with Hooke's Law [duplicate]

Possible Duplicate: Mass points of a Mass-spring model Say I have a spring like the one in the picture below: The point at the top is fixed to a ceiling. The red coloured arrow is the ...
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1answer
133 views

Is There Any Difference Between Strong Quarks Force and Strong Nuclear Force?

the spectrum of quarkonium and the comparison with positronium potential for the strong force is: $V(r) = - \frac{4}{3} \frac{\alpha_s(r) \hbar c}{r} + kr$ (where the constant $k$ determines the ...
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1answer
225 views

Finding the acceleration of Block attached using tricky string setup

Below shown is a setup, and block B starts from rest and moves towards right with a constant acceleration. Does the acceleration differ for the blocks ? I am a bit confused because of the tricky ...
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1answer
878 views

Centripetial Force in Rotating Platform and relation between Period and radius

The experiment setup looks (roughly) like: First, a weight (W2), is hung to simulate centripetal force when the platform is not rotating. Then its removed (W2 is now hanging to one side as shown ...
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1answer
470 views

Torque and equilibrium

I am a little stuck on the concept involved in part b) of the following problem: A $5 m$ long road gate has a mass of $m = 15 kg$. The mass is evenly distributed in the gate. The gate is supported at ...
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1answer
487 views

Calculating torque in a structure

I posted this on math stack exchange but realize it is more a physics question. I have a structure which is set up as shown in the image. A weight hangs from point A with mass $m$. Joint B is free ...
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1answer
300 views

Power, Force Velocity

In any case, if the force and power is constant , does velocity also need to be constant? If no, can you tell me a case. Further can this be extended for non-rigid bodies.
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2answers
97 views

Can a mechanical systems on hold be switched off, in another way than just letting it do it's thing?

Can the value of the potential energy, which is responsible for driving the system, diminish in time, while the system itself is stationary during that time? Can there be dissipation in a system, ...
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1answer
127 views

Why are there two ways to solve for energy of a spring?

I can find the energy of a spring using $F = -kx$, or by using the formula $e = 1/2mv^2 + 1/2I\omega^2 + mgh + 1/2kx^2$. The first way, I get $mg/k = x$, but the second way, I get $2mg/k = x$. Which ...
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2answers
633 views

From where does the force/energy of action-reaction comes from? (Newton's Third Law of Motion)

I was wondering, from where does the opposite force and thus energy comes from when we apply force. For example, lets say there are two persons (P1 and P2) on the universe, and no force is applied to ...
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3answers
336 views

How to imagine the following power and torque?

I can roughly feel a force of 10 newton only by considering the weight of 1 kilogram object. How to imagine the following measurements? Maximum horsepower 16 hp @ 9,500 RPM Maximum torque ...
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2answers
923 views

How to interpret this vertical circular motion problem?

A bucket of water is tied to a rope and swung in a vertical circle. The distance from the bucket centre to the axis of rotation is $2.08m$. Calculate the angular velocity (in $rad s^{-1}$) of ...
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2answers
2k views

Would this model of a boat move according to Newtons 3rd Law?

If i have a small toy boat with a sail, and i attach a fan onto it, FACING THE SAIL, which runs by solar. Once the fan turns on will the boat move or will it remain at rest. Apparently it wont because ...
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1answer
604 views

Can anyone solve this simple static equilibrium problem? [closed]

A bridge is 50m long, has a mass of 20,000kg, and rests on two pivots, A and B. The distance between A and the left side of the bridge is 10m. The distance between B and the right side of the bridge ...
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3answers
271 views

Is $f=ma$ an identity?

In his The Principles of Natural Knowledge, Alfred North Whitehead writes that famous $f=ma$ is an identity: It has been popular to define force as the product of mass and acceleration. The ...
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1answer
177 views

Figuring out the force using Newton's 2nd Law

Here's a problem on my test review: A 12 kg crate resta on a horizontal surface and a boy pulls on it with a force that is 30° below the horizontal. If the coefficient of static friction is ...
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1answer
845 views

Solving an indeterminate triangle truss structure (statics)

From the setup of two trusses as shown in this illustration, how can I solve for the axial reaction forces in the trusses, and in the points A and B (Ax, Ay, Bx, By)? It is assumed that the joints ...
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2answers
2k views

Vertical component of moving weight at a 45 degree angle

Here's an easier one. I use the leg press machine at the gym so I don't have to worrying about hurting myself while lifting heavier weight. The weight glides on a track that looks to be 45 degrees. ...
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1answer
173 views

Is pressure distribution affected by shape

We have two iron (assume real-life stiffness) manhole covers resting on friction-less, perfectly smooth shims on flat ground. One is circular and the other square. If a force F is applied vertically ...
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1answer
196 views

determine temperature at which pita bread will expand in a toaster

suppose you have a pita pocket of radius 5cm or .05m. We will model the pita pocket as consisting of disk with a layer of air of volume V which is contained by the surface of the bread. We will ...
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2answers
2k views

Can someone explain the physics of a standing jump?

I would like to use something like a kinematic equation to know where the person will be in the jump at a given time. However since I think acceleration is not constant because of the jump force it ...
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2answers
463 views

Would a car tow rope withhold an adult person?

I am not exactly sure how the physics work here. If we take a car tow rope, which is manufactured for towing a 3500 kg car and we actually start towing such a car on this rope, what force do we really ...
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0answers
33 views

Is there a newtonian equivalent to Kerr black holes? [on hold]

I would like to follow the off-equatorial trajectory of a test particle around a Kerr black hole. I am interested in two effects: pericenter precession and precession of the orbital plane. I ...
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0answers
10 views

Calculate the distance travelled by hot air before it looses its momentum

Hot air is released from a nozzle with certain velocity into the atmosphere. As the stream travels, it looses momentum and after some time mixes with air.How can we calculate the distance the stream ...
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1answer
36 views

Mathematical misunderstanding of Work-Potential Energy Theorem?

This is a relatively basic question, but I don't understand why it is the case. This is from my dynamics book and is mainly a mathematical misunderstanding. $$ \ dU = F\cos\theta ds $$ Which means ...
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0answers
30 views

Metallic coin over wooden block in glass of water

So there is some water inside a container; the height of water inside the container is $l$. I placed a wooden block on the water and it's floating to some height $x$, on top of the block is a metallic ...
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0answers
21 views

Force and Torque being applied off-center due to magnetic forces [duplicate]

Say that I have two magnetic dipoles, one of which is rigidly attached to a freely movable inflexible body at some point that is not at the body's center of mass, while the other is fixed in space. ...
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0answers
19 views

Is there an applied force acting on the balloon? [duplicate]

A long string is running through a straw with a blown-up balloon taped onto the straw, and a penny taped onto the balloon. There should be a support force going up, gravity going down, friction force ...
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0answers
17 views

Calculating the maximum weight a shelf can hold safely? [closed]

There is a space above the office space that I work in and it has tires stored there. I was told that I would need to post the load bearing amount for OSHA standards. Additionally, our mechanic told ...
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0answers
13 views

What is the total energy? [closed]

So, there was this example in my book with a rock being lifted upwards. The person lifting the rock does 20J of work and gravity does 20J of work. I know Wnet = 0, since there isn't a change in ...
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1answer
29 views

Liquid placed in a rotating cylinder

The Question A closed vertical cylinder is filled with an incompressible liquid of mass m completely. The cylinder is now sealed from all sides and rotated about ...
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0answers
12 views

How to find force acting on ferromagnetic material when it is placed in external magnetic field?

When we bring magnet towards ferromagnetic material ( like iron nails), then material gets attracted towards magnet. Since there is motion of material, there must be force acting on it. How to find ...
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1answer
41 views

Physics Forces and Friction [closed]

I'm working on this problem for my college physics class. It has to do with forces and friction and I want to make sure I go about this problem in the right way. I believe my teacher said that this is ...
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2answers
31 views

Is there a normal downward force here?

Now through my understanding, there is a weight force that points downward on block A, also another weight force that points downward on block B. Between block A and block B, there is two normal ...
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0answers
12 views

Reaction force due to the curvature and gradient drift

We know that a charged particle will have a drift velocity in both a curved magnetic field and when there is a transverse spatial gradient in the magnitude of the magnetic field. This drift velocity ...
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0answers
18 views

Does a pebble create a double torus when hitting water

If you watch slow motion vids of a water droplet or stone hitting water you notice some comes back up. Is this due to some double torus action? There is displacement and some bounce back from the ...
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1answer
53 views

Gravitational work

As far as I know gravitational work is independent from the path of the object, and I have an object that goes up on a inclined plane to a certain height, and than, after the object reaches the edge ...
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2answers
50 views

Work and Free Body Diagrams

I am a bit confused with how to find work when there is a free body diagram. I am trying to work out this problem, and in it a box is being pulled at a constant speed by a rope at a constant angle ...
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1answer
54 views

Calculating the acceleration in a multiple pulley system with one mass? [closed]

This sounded really simple to me at first, but how would you calculate acceleration within a multiple pulley system like this one . I understand that $5T = mg \implies T = \frac{mg}{5}$, but what if ...
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3answers
133 views

Force vs. impulse: what is the math description of their interaction?

Suppose the box (stone, bullet..., $m =1$) is not moving upward because of a lift, but has been shot and has $p = 20 kgm/s, v = 20m/s, KE = 200 J$ Gravity is doing negative work and subtracting ...
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1answer
26 views

two bodies are travelling with equal acceleration

two bodies are travelling with equal acceleration in the same direction and are in contact with each other. What will the force exerted by 1st body on second be? By taking an example of masses 5 and ...
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1answer
23 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 ...
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0answers
31 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 ...