# 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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### Rod in zero gravity pushed

Imagine a rod - an ideal line segment of some length $l$ - is in zero gravity and initially no force is acting on it. Then something hits it and it gets some impulse $p$ in some location along the rod ...
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### The classic falling rope problem

A rope was on top of a table with a part of it hanging off the edge, without any friction. The equation of the motion is: \begin{equation} \frac{mgx}{L}=m \frac{dx^2}{dt^2} \to \ddot{x}=\frac{gx}{L} \...
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### A basic question on friction

Suppose A and B experience friction with each other but they move on a smooth floor. A is given a force F which is not enough to overcome friction; a frictional force equal to F, thus, acts on B. Now, ...
18 views

### Block on Block Problem with Friction on both surfaces [closed]

Consider two blocks, one on top of the other on a rough table, with masses m1 and m2 respectively. (m1 on top of m2) Coefficient of friction between the blocks is μ1 and coefficient of friction ...
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### Direction of kinetic friction in rolling with slipping

When a ball rolls down without slipping on a ramp, the static friction is pointing upwards along the ramp, providing the torque for rolling. No problem with that. However, if a ball has initial ...
62 views

### 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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### 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 ...
448 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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### 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 ...
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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 ...
32 views

### 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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### 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 ...
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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 $q_1$?
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### 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 ...
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### 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 ...
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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
1 vote
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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, ...
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1 vote
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### 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
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### 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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### 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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### 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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1 vote
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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 ...
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### 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 '...
1 vote
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### 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
51 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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### 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 ...
1 vote
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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, ...
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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 ...
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### 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 ...
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1 vote
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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,...
1 vote
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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 ...
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1 vote
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### How do we define the orietation of a particular frame of reference? [closed]

I think my question will be clearer if I take some examples: Find the acceleration with which a block slides down a frictionless slope. For this problem the free body diagram for the block would ...
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### Can you fall in a Gravitron centrifuge ride?

I went on a Gravitron ride with my 5 year old son. He became "hysterical" with fear and started pushing himself off the wall. I my arm across his body trying to keep/push him back as he was ...
56 views

### Can we conserve angular momentum in pure translation motion?

suppose a block is moving on a surface with velocity v paraller to the surface. the surface is rough and is exerting some frictional force on block. consider the point 'O' in above image. since net ...
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1 vote
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### Why does Newton's third law not cancel out when a force pushes one object against another? [duplicate]

For example, I have a force of $3N$ accelerating a $1$kg block $A$ on a frictionless surface to the right. $A$ accelerates at a rate of $3$ $m/s^2$. Say it collides with another block $B$, weighing $2$...
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### How do you account for the weight of the lever?

I have a 6 foot lever where the fulcrum is 2 feet from the input force. In an ideal situation, this gives a mechanical (dis)advantage of 0.5. However, let's just assume there is no weighted object ...
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### Applied force vs restoring force [closed]

Let us take a horizontal spring block system where the block is initially at the mean position. If we pull the block applying a force $F$,then by Newton's $3rd$ law,the block will pull us by the exact ...
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### When a spring is held from one end and some mass is put on the other end and it's rotated then why does it get stretched? [duplicate]

While going through a question I found that if we hold a spring from one end and rotate it then it gets stretched. One explanation may be that centrifugal force is acting on it...but if I want to ...
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### Why does Centripetal Force seem to be unbalanced?

You'd think it would have an opposing force due to Newton's Third Law, but it is usually portrayed alone, without any other force there cancelling it out. I know there exists a concept of Cetrigufal ...
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### How come the friction is directed upwards (the one that will arise from the vertical wall)?

Well as you can see in the image, the problem involved drawing the free body diagram of the system when a force $F$ is applied to the disk which is stuck between a rough vertical wall and a ...
51 views

### Direction of static friction in an inclined plane [closed]

Let us suppose an object is placed on an inclined plane. Let us also assume the surface has a coefficient of static friction $\mu$. The object is being pulled by a force $F$. As a result, the object ...
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### What is the meaning of the statement"centre of mass of a body remains in equilibrium"?

Explain the meaning of statement"centre of mass of body remains in equilibrium if total the total external force on the body is zero".what is exactly meant by the term equilibrium here?
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1 vote
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### Acceleration of wedge and mass locked on axes [closed]

Consider this diagram: Mass m1 can only move in the x direction and mass m2 in the y direction. Find the acceleration of both m1 and m2, and the reaction of the wedge. Negligible Friction. I tried ...
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### Moment and forces in joints

Can anyone help me understand the significance of the forces in joints? My method: Let FG be tension T, force at D be D parallel to y-axis, force at B be B parallel to y axis Taking moment about B ...
1 vote
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### Maximum acceleration without tipping over - torque balance analysis on an non inertial reference system

edit: This is not a homework question, but a question about whether choosing a different rotation axis can affect the torque balance analysis. I am just using the following example to illustrate ...
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### Newton's 2nd Law for car on a highway

So I was trying to get the equations of motion of a car driven on a highway and that is affected by drag (other dissipative forces are neglected) via the use of Newton's 2nd Law. I supposed that the ...
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1 vote
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### What is physically going on when I stick my finger in a glass of water and the scale tips downards implying it got heavier?

Suppose I have a scale with a glass of water on one side and a counterweight on the other side. If I stick my finger in the glass of water I observe that the water side of the scale becomes heavier ...
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### Bottom point being at rest in pure rolling

We know that,in rolling without slipping,the point of the disc of radius $r$ which is in contact with ground,has two velocities acting on it. One is the linear velocity of center of mass \$v_{\mathrm{...
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1 vote