Questions tagged [free-body-diagram]

A pictorial device which analyzes forces present on any body with the use of vectors. Allows easier grasping of problems involving either objects at equilibrium or in motion. Can be used to predict presence of forces.

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Understanding coordinate system for looping pendulum equations of motion

I'm interested in the phenomenon of the looping pendulum, which is a system consisting of one large and one small mass connected by a string passing over a rod. In particular, I've been looking at ...
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1 answer
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Components of weight while banking

If I have a plane thats banking, am I right in saying that the centripetal force pulls it towards a centre. What happens to weight? I understand that it breaks into parallel and perpendicular ...
2 votes
2 answers
438 views

An object is being swung around in a circle, attached by a string. If the string breaks, does the angular velocity instantly drop to zero?

If an object attached to a string is being swung around in a circle, then when the string breaks, the object will continue in a straight line at a constant velocity, per Newton's First Law. If I ...
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1 answer
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Forces Problem from Halliday, Resnick and Krane [closed]

To my knowledge, the net force on $m_1$ is $T - m_1 \cdot g \cdot \sin(\theta_1) = m_1 \cdot a$ assuming that the block accelerates up the incline. However, the solutions manual states that the ...
0 votes
1 answer
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Will parallel spring balances vs single spring balance with same mass give the same reading?

So, if we have two identical spring balances and attach a 1kg mass, and then take another 1 kg mass and attach it to one spring balance, will we get the same reading? I tried to draw free body ...
3 votes
5 answers
113 views

Pascal's law further simple proof for students of an high school

Pascal's law states that a force applied on a surface of a fluid is transmitted within the fluid in all directions of the fluid with the same intensity on equal surfaces. Similarly, it can be stated ...
0 votes
1 answer
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Calculating spring forces, when springs are angled

I am working in a game engine on basic suspension using springs. I have nothing further than high school physics, so excuse the question is its basic. I am learning. For example, a motorbike is a ...
174 votes
21 answers
150k views

Given Newton's third law, why are things capable of moving?

Given Newton's third law, why is there motion at all? Should not all forces even themselves out, so nothing moves at all? When I push a table using my finger, the table applies the same force onto my ...
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0 answers
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Forces in a rope (tension) [duplicate]

I am confused with the concept of tension in a rope. Look a the diagram. Two forces are acting in a body, in this case the body is a rope, hence the total force in the rope should be zero, right? So, ...
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2 answers
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Coulomb's law: Is $F_1$ equal to $F_2$ even if $q_1$ is not equal to $q_2$?

I am learning the Coulomb's law. So I have question, If $q_2$ be 4 times more than $q_1$, would the force from $q_1$ to $q_2$, still be equal to the force that pushes from $q_2$ to $q_1$?
2 votes
2 answers
162 views

Is the normal force the reaction force?

There is a box on the surface of earth. The earth exerts a force to the box (black arrow). The box exerts a reaction force to the earth(brown arrow). But this reaction force is exerted to the earth ...
21 votes
9 answers
12k views

Does the weight of an hourglass change when sands are falling inside?

An hourglass H weighs h. When it's placed on a scale with all the sand rested in the lower portion, the scale reads weight x where x = h. Now, if you turn the hourglass upside down to let the sand ...
2 votes
4 answers
172 views

Tension in massless rope

We are learning Newton laws in the University and were given the following problem: In the system described in the image, the man is pulling two massless ropes with a force of $F$ each. We are ...
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1 answer
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Why is this system isolated?

(Image updated for clearance) Hello, Assuming that there is no friction anywhere and both box 1 and ramp 2 start at rest, I was wondering why this is an isolated system in terms of momentum ...
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2 answers
36 views

Solving for forces up a slope [closed]

This is a problem from my physics homework that my teacher did not explain. I still do not understand, so I was wondering if someone could help me out. Problem: A $50$kg box is being pushed up a $45^{...
2 votes
3 answers
543 views

Can you determine an action-reaction pair when tension acts on a string attached to a pulley?

I have been learning about tension and was doing some reading on trying to explain these forces at the intermolecular level and later also trying to see how it fits in view of Newton's third law- I ...
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1 answer
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Two forces act on a body as shown [closed]

Two forces act on a body as shown on the grid below. Draw a scale diagram to determine the resultant force acting on the body. Use a scale of 1 cm to 1N
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1 answer
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In simple terms, why does a skateboard slide in the opposite direction of its falling rider?

I would like to have a better understanding of something I’ve observed: If I stand on a skateboard at rest, there is no movement. If I lift my left leg, my body of course starts to fall to the left, ...
0 votes
2 answers
365 views

Choosing signs in free body diagrams of subsystems

In an example problem from a book I'm using (David Morin's Introduction to Classical Mechanics with Problems and Solutions), there is a system with a person and a pulley on top of a platform. The ...
1 vote
2 answers
65 views

How do Parabolic Flights exactly work?

I understand how one can feel weightless in an elevator - in the person's reference frame, they are not being pushed up by the floor. However, I don't understand how this can occur in parabolic flight....
1 vote
3 answers
87 views

Solving a problem regarding a block sliding down a ramp [closed]

A body of mass $5×10^{-3} kg$ is launched up a ramp making a $30°$ angle with the horizontal, and it takes twice as much time to slide down than it took to get to the top, find coefficient of friction ...
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1 answer
122 views

Tension Problem (Classical Mechanics) [closed]

An exercise from my textbook revealed to me that I have some misconceptions about Newtonian mechanics. The textbook gives the answers to the questions, but I'm hoping someone can explain how it works ...
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1 answer
182 views

Reactive force on two objects with central forces

I have a confusion with reactive forces, in how they act, and I hope to highlight my confusion with some (very) poorly drawn graphics by me. From my understanding (likely false), a Newton's Third Law ...
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5 answers
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Uniform circular motion in vertical plane: Free body diagram confusion

I'm considering the free body diagram for an object attached to a rigid rod undergoing uniform circular motion in a vertical plane where the net force acting on the object must always be acting ...
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2 answers
296 views

Can I know if an object will slip or will accelerate forward when it is pushed by a force that exceeds the maximum force of static friction?

If we push a trash can, it will not move until we exceed the maximum force of static friction, but when we exceed the maximum force of friction, will the can slip or accelerate forward?
1 vote
1 answer
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Friction forces in an idealized model of hydroplaning

I am reading this question from this text I am not sure how to write the friction force in terms of the contact area $A$, speed $u$, mass $M$, viscosity $\mu$ and thickness $h$. The friction force as ...
0 votes
1 answer
31 views

What would be the FBD/external forces on the floor of a lift moving with acceleration a downwards?

We know that external forces are held responsible for acceleration produced and we represent external forces on a choosen system using FBD. For the case of an life moving downwards with acceleration '...
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2 answers
151 views

Is the sectioning in method of sections, for truss analysis, arbitrary?

I was looking through a lot of sources about the method of sections. But the thing that stood out to me was that everyone sections a truss such that at least one of the supports, and therefore at ...
1 vote
1 answer
812 views

Eccentrically loaded bolts in which the plane of loading is parallel to the bolt plane

This are eccentrically loaded bolts in which the plane of loading is parallel to the bolt plane.When deriving an equation to this particular problem almost all books start by assuming that $$\frac{F_{...
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4 answers
934 views

Bending of a cyclist while taking a turn on a horizontal road

I am a high school student and my teacher taught me that a cyclist bend while taking a turn on a horizontal road because if he doesn't bend it then it will rotate due to net torque of friction about ...
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1 answer
449 views

How come at a certain joint a truss is a zero force member and at another is isn't?

I have a slight confusion regarding zero force members. I'm analyzing a structure and I started at joint E and found that truss GE has a force of 8.4 [kN]. However, if I analyzed it at joint G, I can ...
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0 answers
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How is energy transferred among particles of a body when we give some kinetic energy to it? [duplicate]

When we say a body is given kinetic energy $\frac{1}{2}mv^2$, what do we mean by this? Is this energy transmitted to all the particles of the body uniformly? If not, Where is this energy stored?
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2 answers
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How does surface tension prevent a pin from sinking?

Please explain simply how surface tension in water which as far as I understand is a force pulling the water molecules at the surface towards each other horizontally so how does that prevent a ...
1 vote
2 answers
46 views

Additional force on a scale [closed]

I have this problem I solved, but I don't think I understand in full detail. I think the underlying physics concept here is the change of momentum in a system where mass is changing. A person is ...
1 vote
1 answer
50 views

Virtual work method in pulley [closed]

The problem illustrates two pulleys whose two ends are going downward with velocity $v$. The problem was about finding the velocity of the point $X$ i.e the point where the strings of the two pulleys ...
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1 answer
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Work done on person standing on an escalator

Say a person stands on the escalator which is going downwards. The normal force by the escalator does negative work, and the gravity does positive work. The person apparently loses some potential ...
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1 answer
209 views

What does a scale accelerating on an incline read?

I was watching an online video lecture about dynamics, and then I came across this brain teaser, and I've been thinking it over for a couple of hours but can't seem to find the solution. I hope ...
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3 answers
644 views

How can we know direction of blocks in pulley systems?

How can we find the direction of acceleration in pulley systems so that we can write equation of motion for different parts of the pulley system. Do we have to assume acceleration in some particular ...
1 vote
3 answers
1k views

Forces in a staically determinate cantilever Truss, why some experiences compression while others experience tension?

The Redundant Truss Apparatus is constructed with units of basic triangular pin-jointed. At joint 1, it is fixed firmly due to a support. At joint 2, it is fixed to a movable support. Suppose at ...
2 votes
2 answers
284 views

Working with ramps and rotational acceleration (friction involved)

Say you have bicycle tire moving with constant velocity. Since the point of contact with the surface remains stationary, so tire will not slide even on an icy surface. But if pushed tangentially to it ...
0 votes
1 answer
202 views

Does the rope stretch when the pulley of Atwood's machine is accelerated?

Let's say I've an Atwood's machine in which I have two point masses which are different. Now, when I accelerate the pulley, the two masses accelerate at a different rate which can be shown by ...
1 vote
2 answers
241 views

Applying newton's second law on circular motion

In school, when we are studying circular motion, we analyse the forces acting on the body into two axis, the tangential one to the speed of the body and the perpendicular one and then we apply newton'...
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1 answer
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Question about applying Maxwell's Equations to analyze a copper shaft and magnetic bearing

fellow physics people I have a question regarding the mathematics behind how a magnet will slow down as it falls through a copper pipe. I am aware of the mechanism in which this works, the falling ...
1 vote
1 answer
7k views

How does centre of gravity influence the equilibrium?

Ok! This really makes hard to think, how does a single point determine the object's equilibrium? If an object is displaced from its equilibrium-position & if the equilibrium is stable, the object ...
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3 answers
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Newton's 3rd law and falling bodies in air - a little confusion about action/reaction

According to this law, a 1 ton block of metal falling in air will exert a force of 10N on every single molecule in the air. Let's simplify and take 1 single such molecule. The 1 ton block exerts 10N ...
1 vote
1 answer
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Friction coeffecient between two stacked blocks moving at constant velocity [closed]

So I came across a problem, it says that there are two masses, $m_1$ and $m_2$, stacked on top of each other, and they are moving at a constant speed. There is also friction between the two blocks, ...
0 votes
2 answers
58 views

Work done by me and Kinetic friction

What will be value of work in following cases. I move a box on a rough floor in a straight line for a distance 'd' from A to B then B to A back. 1- Is work done by me= 0? as displacement=0 (is that ...
1 vote
0 answers
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What type of force is applied to an object when we push it? I am talking about the net force [duplicate]

what I mean... If net force applied by my hand to box is contact force then should not the box apply same magnitude of contact force on my hand and the box will remain still [These forces are in pair,...
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If net force applied by my hand to box is contact force then shouldn't the box apply same magnitude of contact force on my hand? [duplicate]

Wait,what I mean here is,if I applied contact force with my hand and it pushed the box,then the box,as said in 3rd law,should push my hand with same contact force. The point is,if net force applied by ...
1 vote
6 answers
799 views

Can force be applied without accelerating?

When I push against a wall, I am applying force on the wall and the wall applies an equal force against mine therefore the wall doesn't move and neither does my hand. But isn't acceleration required ...

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