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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 [tag:particle-physics] for decay channels due to forces and [tag:newtonian-mechanics] or ...

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What is the proof for the thrust force formula of a jet engine?

Is the thrust force in a jet engine equal to the difference between the product of mass flow rate and velocity at the entrance -the product of mass flow rate and velocity at the exit. I was reading a ...
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1answer
28 views

Work done on box

I am having a hard time grasping this. W = Fd = mad, and given v vs t graph, the area under the curve will give us d. When the velocity graph draws a horizontal line, a=0. Thus I thought that A = C ...
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28 views

Predicting Rotation vs Sliding Forwards when Pushing an Object

Suppose there is a cuboid object sitting on a table, and a force is then applied to it. This figure shows the top-down view: I am curious to understand how the object will move due to this force, ...
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0answers
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stability of a mine tailings dam

re less than hydrostatic, that is, the material does not transmit forces in all directions such as a liquid with a hydrostatic head would. Then a decision is made to raise the tailings dam, (increase ...
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1answer
26 views

Using Euler equations to solve for torque

I am trying to solve the torque needed to rotate a rectangular plate of sides $a$ and $b$, about a diagonal with constant angular velocity $\omega$. Euler equations are given by, $$ I_1\dot{\omega}...
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Work Strain Force [on hold]

A bungee jumper of mass $70\thinspace\mbox{kg}$ stands on a platform $25\thinspace\mbox{m}$ above a river. He has a light linear elastic bungee cord with coefficient of elasticity $153\thinspace\mbox{...
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Centrifuge Artificial Gravity?

I just saw the following video: NASA centrifuge. In video, a person is walking on a huge spinning centrifuge. But his weight is still acting downwards and there is no supporting force which will keep ...
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2answers
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Block wedge system why does the wedge move at all when the block moves shouldn't the normal forces cancel out each other?

In a Block and Wedge system if the block is kept on a wedge and the block remains at rest then so does the wedge in the ground frame due to Nsinx components cancelling out on the block and the wedge. ...
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1answer
20 views

Pressure increasing with depth work for directions other than downward

How does pressure increasing with depth work for directions other than downward? Can you explain this on the macro and micro level? I get how it works on a macro level for downward forces because ...
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4answers
42 views

Springs and Hooke's Law

Suppose a mass was stretching a vertical spring. Why does the mass have a velocity in its equilibrium position where the net force is 0? Note the spring is massless.
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0answers
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The effect of fixed pulleys on weight at 90 degrees

If you have a fixed point pulley, and you are pulling a rope attached to a 100kg weight, how much weight are you pulling at a 90 degree angle? ...
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29 views

Question on pendulum and the time needed for it to stop [on hold]

A pendulum of $1\ \rm m$ length with a mass of $1\ \rm{kg}$ is displaced by $10^{\circ}$ and released with zero initial velocity. Neglecting the weight of the rope, calculate the time required for ...
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Clarification regarding the banking of roads [on hold]

My question is regarding the banking of roads. The equation provided by most textbooks to find the maximum angle of banking is $$\tan \theta = \frac{v^2}{gr}$$ I am confused as to what $r$ ...
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0answers
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Help with a physics problem [on hold]

A 5 kg box sits at rest on top of a 10 kg box that is at rest atop a flat surface. A 40 N horizontal force is applied to the 5 kg box for a period of time. The coefficient of kinetic friction ...
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1answer
34 views

What forces the maximum speed of a cyclist on a steep climb?

I know that on a flat road drag is the main force, I have to provide as much force as the drag (and the friction in the drive train) produces. I can also see that the faster I ride, the harder it gets ...
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2answers
48 views

Newton's third law in a two body system

If I push on a table with some force 'f' then by newtons third law of motion the table also applies the same magnitude of force on me in the opposite direction. I get that there may be various forces ...
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5answers
703 views

Is the normal force equal to weight if we take the rotation of Earth into account? [duplicate]

In my physics class we were doing problems such that we set $N$ (normal force) $= mg$. I understand that by Newton's Third Law, if I exert a force on the ground, then the ground will exert an equal ...
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2answers
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Finding the value of the holonomic constraint forces

So let's say I have a Lagrangian augmented with some holonomic constraints. $$L' = L + \sum_i \lambda_i(t) f_i(q,t).\tag{i}$$ The solutions is the system of differential equations: $$\frac{\partial ...
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0answers
21 views

Impulse and force [on hold]

A metal ball with mass $40.0\ \rm g$ is dropped from a height of $2.00\ \rm m$ onto a horizontal metal slap.The ball rebounds to a height of $1.60\ \rm m$. Calculate the impulse delivered to the ball ...
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2answers
84 views

What is function of force $F$ and work $W$?

I know that : Position $$r:\mathbb{R} \to\mathbb{R^3} \ \ \ \ \ ; \overrightarrow{r}(t)$$ Velocity $$v :\mathbb{R} \to\mathbb{R^3} \ \ \ \ \ ; \overrightarrow{v}(t)$$ Acceleration $$a:\mathbb{R} \...
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1answer
25 views

A rod with a ball attached is balanced?

An object is made by hanging a ball of mass $M$ from one end of a plank having the same mass and length $L$. The object is then pivoted at a point a distance $L/4$ from the end of the plank ...
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1answer
23 views

Why does the vector in the banked turn problem not point to the center?

I am currently working on the banked turn problem. I know that once you set up all the equations properly you end up with $$v^2=gR\tan{\theta}$$ I drew a little diagramm of the forces: I know that ...
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2answers
56 views

Calculating the force on a bike chain idler sprocket

I am trying to get a rough estimate of the force on an idler sprocket in a bike chain line, in order to get bearings robust enough for the task. Assuming a chain tension of 150 pounds and an idler ...
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1answer
50 views

Why is the work done the same in this case? [on hold]

The formula for work is $W= Fd \cos \theta$. A body, which is pivoted at point P, and wherein force is applied at point F1 first and then at point F2, rotates from position 1 upto position 2 in both ...
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0answers
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If you set crates of different masses to the same initial velocity, which one will stop first and which one will have the greater displacement? [closed]

If you set two crates of different masses to the same initial velocity, which one will take the longest amount of time to come to a stop? Which one will travel the longest distance? Which one will ...
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1answer
52 views

Is Gravity still considered to be part of the “Superforce” which existed at the instant of the “Big Bang”

My limited understanding of the Big Bang is that all the Fundemental Forces (Electromagnetic, Weak Nuclear, Strong Nuclear and Gravity) were originally part of a "Superforce." As the universe cooled ...
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0answers
24 views

Tension in a rope pulled equally on both sides [duplicate]

I would really appreciate it if someone can help me understand Newton's third law as it applies to the tension in a rope involved in a game of tug-of-war with 0 acceleration. Disregarding friction, ...
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3answers
106 views

Why equation $F = m a$ is not valid in relativistic physics but $F = dp / dt$ is valid?

I read that the equation $$F = m a$$ is not valid in relativistic physics. Instead $$F = \frac{d }{dt} \frac{mv}{ \sqrt{1- \frac{v^2}{c^2} } }$$ is valid in relativistic physics but why is that?
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1answer
45 views

How does an object in space travelling at constant velocity have a net force of zero acting upon it?

If the definition of balanced forces is "two opposing forces that are equal" and an object with a net force of zero acting upon it means that the forces are balanced on the object, then it should ...
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1answer
52 views

Rod that is toppling over

A rod is about to fall over. If $N=mg$, then there is no resultant vertical force acting on the object. So how is the object able to fall over? Intuitively I understand why it would fall over but ...
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0answers
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Calculating string force [closed]

A mass $M=8\ \rm{kg}$ is being pulled upward by a rope of mass $m=2\ \rm{kg}$, and its acceleration is constant and equal to $2\ \rm{N/kg}$. Calculate the string force: a) at the highest part of ...
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1answer
29 views

Find impulse provided by the stopping object [closed]

I have tried to understand this problem, but I'm still struggling with it. a 27g bullet hits a piece of wood and goes in 8.6 cm. if the bullet stopped in 0.44ms. what impulse did the wood provide?
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1answer
35 views

How is the acceleration proportional to the net force over the mass? [closed]

The acceleration is inversely proportional to the mass when the force is constant. Also, the acceleration is proportional to the force when the mass is constant. So, how can the acceleration be ...
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6answers
101 views

How can static friction depend on the normal force, but be directed orthogonal to it?

According to my understanding: two orthogonal forces aren't related and two orthogonal vectors don't affect each other the force of static friction $F_s$ depends on the normal force $F_n$, so $$F_s = ...
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0answers
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What is the force required to drag the block B leftwards? [closed]

with accordance to the figure given below what is the magnitude of force required to drag the block B leftwards??
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1answer
55 views

Can Pseudo force be used for the monkey B [closed]

Monkey $B$ is holding on to the tail of monkey $A$, which is climbing up a rope. The masses of the monkeys $A$ and $B$ are $5 \; \text{kg}$ and $2 \; \text{kg}$ respectively. If $A$ can tolerate a ...
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0answers
27 views

Static friction force between truck's wheels and road [closed]

Alright, so I have this stupid problem which I cannot seem to solve, and I think I have insufficient information. We have this truck. Some insane guy wants to bike on that wall. After some attempts,...
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0answers
19 views

the effects of wind on particles trapped in a laser beam

First off I have done a few experiments with trapping of particles in a laser beam using a red 100mW laser and a 532nm 20mW laser. The Setup to achieve the two is seen below. Now in real life you can ...
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2answers
55 views

Ambiguity in d'Alembert's principle

It seems to me that many different momenta $\dot{\bf p}_j $ can satisfy d'Alembert's principle: $$\tag{1} \sum_{j=1}^N ( {\bf F}_j^{(a)} - \dot{\bf p}_j ) \cdot \delta {\bf r}_j~=~0 $$ in a ...
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1answer
54 views

How do I calculate the maximum force needed to apply on the structure for it to topple over? [closed]

The structure consists of 6 parts as shown and the purpose of this structure is to be placed in construction sites to monitor the progress of works. As such, the structure will be subjected to ...
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2answers
42 views

Power by normal force

Would the power created by the normal force always be zero? Since normal force is always perpendicular to the object?
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1answer
24 views

Plane Vs Train Solely on Energy Effeciency [closed]

To be fair I am not sure if this is the right SE for this but I couldn't think of a better one: Ignoring the cost and types of their respective fuels, which of two forms of specified transportation ...
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0answers
18 views

Why don't I accelerate upwards due to reaction force? [duplicate]

Now I am standing on the ground and thinking that I exert a force equal to my weight on the ground. So as a reaction the ground also exerts a equal reaction force on me of the same magnitude and ...
1
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2answers
76 views

Does free fall ever occur on the surface of Earth?

According to the definition of "Free fall", which is "Downward movement under the force of gravity only.", free fall only occurs when gravity is the only force acting on an object. But here on Earth, ...
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0answers
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How do I account for end effector orientation during calculation of theoretical suction force?

This is in context of a robot whose tip is attached to a vacuum gripper. The theoretical holding force of a vacuum gripper is given by, $$ F_H = m*(g+a)*S$$ which is, $$F_H = (F_g + F_a)*S $$ where,...
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1answer
21 views

Is a perfect infinite range interactions the same thing as no interaction at all?

By perfectly infinite range I mean a potential which is a constant, no matter the distance. Would one just recover a single-particle behaviour? Whatever any particle does, everything else has to ...
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2answers
481 views

Car and truck collision

When a car and a truck crash, the car seems to get damaged a lot more. Why does the car get more damaged then the truck in the collision?
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0answers
24 views

Vertical loop forces [duplicate]

So my buddy and I were playing roller coaster tycoon, and we were thinking about the physics behind a cart going around a loop. So we could think of the forces pretty easy for a loop on the x axis (...
4
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2answers
42 views

A question about magnets, energy, and forces [duplicate]

Following my first lecture on magnetism today, I'm left with just one question my lecturer couldn't answer. Imagine a 1 kg magnet supporting its own weight stuck to a vertical surface, resisting ...
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0answers
50 views

How does one solve for the tension force on a DIAGONAL circle? [closed]

I dont seem to see any solutions on the web. Only horizontal and vertical circles are available. Also, how does this diagonal circle formula apply when the string is slack and the centrifugal force ...