# Tagged Questions

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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### Problem with finding the force of when an object falls from freefall and hits the ground

I am trying to find the force of an object hitting the ground in terms of its weight, $w$. I set up the problem, but I know I am not getting the right answer. Imagine you are released from rest 2km ...
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### Can two bodies of different mass attached at ends of string passed over a frictionless pulley produce equal tension on both sides?

In my textbook there is given a case that to calculate acceleration and tension produced in string when string is attached at it's ends with two bodies of masses such that $m1>m2$ and the tension ...
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### Confused about Newton's 3rd law

I am confused about Newton's 3rd Law. If a person jumps off the ground a force is applied both to the person and to the ground. However, as $F=ma$ acceleration experienced by the Earth is much less ...
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### Why do riders feel forced down into their seats at the bottom of the first drop on a rollercoaster?

I am trying to figure out what forces an $80.0kg$ rider travelling at $110.0km/h$ ($30.56m/s$) would experience when at the bottom of the first drop on a rollercoaster where the radius of the ...
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### Tension of three ropes [on hold]

How can I calculate the tension of something with three ropes? I tried a lot of things and I didn't succeed.
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### 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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### Moment of Inertia of 'U' shaped rod hanging from celling [closed]

The ends of three identical uniform thin rods are joined at right angles to form a U-shaped body. A freely rotating axle $A$ is attached to one end of this body. The axle is then fixed to the ceiling ...
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### Determining direction of static friction when tension and gravity are present

I'm a private Physics tutor, and I'm a bit stumped by one of my student's problems. It's #3 on this worksheet (http://www.hopewell.k12.pa.us/Downloads/Inclined%20Plane%20Worksheet.pdf -- not his ...
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### in Newtons 3rd law, where does the second body get its energy to react?

A very basic question, and apologies if I have overlooked something obvious. In newtons 3rd law, presumably energy is transfered to the second body from the first body (which itself was subject to an ...
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### Is gravity a force and if so what is its opposite?

For every force there is an equal force in the opposite direction on another body, correct? So when the Suns gravity acts on Earth where is the opposite and equal force? I also have the same ...
40k views

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

I've got a rather humiliating question considering newton's third law "If an object A exterts a force on object B, then object B exerts an equal but opposite force on object A" -> $F_1=-F_2$ ...
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### Why do objects move when you apply a force that's equal in magnitude to the friction? [duplicate]

If the friction on an object is 200 N and you apply 200 N, it seems, the forces should immediately cancel each other out since the friction and your applied force go in opposite directions, leaving ...
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### Problem in constraint equations

In this, if I want the acceleration constraint between $M$ and $2M$, I write $AM+2AB$=LENGTH OF STRING, which on differentiating twice gives $a_{m}=2a_{2m}$(which turns out to be correct). However, ...
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### Does air resistance give a falling skydiver weight?

An observer in free fall is weightless as he is accelerating at 9.8 m/s^2. However, when a skydiver jumps from a high plane, his acceleration gradually slows until becoming 0 m/s^2 at terminal ...
621 views

### Why can't I push myself in a chair? [duplicate]

If I am sitting in a chair with wheels and someone pushes on the back of my chair with sufficient force it will role along the ground. However, if I push on the back of the chair with the same force ...
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### Why are inclined push-ups harder?

I came up with a random question which looked simple, but I can't work out the answer. The question is, why are inclined push-ups harder? And by inclined push-ups I mean push-ups with your legs on a ...
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### 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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### If the force of friction is 20 N for a moving body does acceleration increase with the increase of the mass?

A body is moving and the only force acting on it is the force of friction. If we put another body on this moving body somehow the force of friction will increase; does its acceleration change?
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### Pulley-rope tension question

I'm learning mechanics and I don't understand the following (simple, I guess) concept. Here's a pulley-rope system: The force of tension, as I understand it, is defined as the force exerted on an ...
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### A question on Newton's laws of motion [closed]

A force of $50N$ is required to push a car on a level road with constant velocity of $10m/s$. The mass of the car is $500kg$. What force should be applied to make the car accelerate at $1m/s^2$? I ...
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### Horizontal and vertical acceleration of a ball on a slope?

I understand that you resolve the components of the balls weight parallel and perpendicular to the slope in order to calculate the force due to gravity that actually acts down the slope. The ...
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### Will the normal force will be different if there is different area of contact?

Let us say 2 soild frustum of height h and having different radius $r_1$ and $r_2$ respectively where $r_1\>> r_2$ having mass same. There is one one frustum which is kept on ground vertically ...
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### How does Newton's third law apply to an object interacting with air?

We all know that if I punch the wall with $100\,\mathrm{N}$ force, the wall pushes me back with with $100\,\mathrm{N}$ and I get hurt. But if I punch air with $100\,\mathrm{N}$, does air punches me ...
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### Spinning an object in vertical circle

The situation : A block of mass $M$ is tied to a string and is spun around in a vertical circle. The question asks me to calculate the tension in the string 'at the lowest point' after giving ...
2k views

### How does friction and mass of the string influence the tension force?

According to my book, "tension is the reaction of a rope when it is stressed". Then it also said when the string is massless, tension is same everywhere. However in a,let, pulley-rope system,when ...
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### Motion on inclined plane

What has to be the conditions for an object of mass $m$ to move down an inclined plane with uniform velocity in terms of the forces acting in different directions on the object?
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I disagree with the answer to this homework question. Here it goes. The coefficient of static friction is 0.60 between the two blocks in figure. The coefficient of kinetic friction between the ...
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### How to draw a formal free body diagram for a object at rest on a inclined plane?

Five choices I made up: a. b. c. d. e. One thing I know immediately is that the vectors have to cancel each other at last so there is no net force acting on it. a. certainly ...
343 views

### Question about a car on a banked turn with no friction

A popular physics page explaining how a car can make a banked turn even with no friction : gives the following free body diagram and then says In the vertical direction there is no ...
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### What does the free body diagram for mass 1 look like?

In this situation: Enough tension is applied towards the right on $m_2$ so that $m_1$ starts sliding backwards. I am confused about what the free body diagram for $m_1$ looks like. Here is my ...
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### How to write the moment equation about a rotating as well as translating point?

I want to write the moment equation in Ground frame as well as the frame of reference of the point (which I think should be a rotating frame of reference) for the following situation. $C$ is the ...
32 views

### Help interpreting diagram of compressive forces in bone

I am trying to understand where I should draw my arrows for a free body of the following picture But I've never tried to draw free body diagram to explain these kinds of curvy lines. I think if I ...
1k views

### Why doesn't a wall move when you push it if there's space behind it?

In the first screen you can see that if a person were to push a wall within a typical household the wall would not move while keeping themselves tractioned to the floor. If you push hard and do not ...
260 views

### Centripetal force on a Ferris wheel

(This is a high school–level problem, so no air resistance, etc.) A person is sitting on a Ferris wheel of radius $r$ moving at a constant speed. What is the force from the seat acting on the ...
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### Why is it effectively impossible to balance this rectangle block on a triangle block? (See photo)

I've always wondered why it's basically impossible to balance a rectangle block on top of a triangle one like this. This is my nine-year-old giving it a try. I have never in my life gotten it to ...
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### Is it wrong to equate the net force to the force by the spring to find its maximum expansion?

When I want to find the maximum expansion in a spring, let's say connected to 2 blocks of different masses, and some force is applied on one of them, I find their separate accelerations and then ...
134 views

### Vertical circular motion: minimum velocity

In vertical circular motion while finding the minimum velocity at the bottom-most point for looping the loop, why do we take the tension at the topmost point to be zero?
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### What are the forces acting when we squeeze a ball? Free Body Diagram?

As part of my project, I am trying to figure out the forces acting while squeezing a ball. The ball in question is a foam rubber ball (stress ball). The ball deforms when we squeeze & the mode of ...
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### Question about solving Newton's laws' problems [closed]

A questions from my textbook asks me what the force by the pulley on the roof is. In order to answer the question, need I consider those objects hanging from both sides of the rope, or need I only ...
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### Pulley system: how can tensions be equal throughout a entire rope if the weights on opposite ends are different? [duplicate]

More weight means more pulling force, and thus more tension force. Like this answer says, however much force you pulling with is equal in magnitude to the tension force. If that is case, how then ...
359 views

### Acceleration of a ramp

If we have a ramp and a block on it, and if all the surfaces are frictionless so both the the ramp and block can move. Is the normal force different from the time that ramp is not moving? If yes can ...
108 views

### Reduced-gravity flight (A300 0-G): what is actually reduced?

I doubt I can hide from the effects of gravity when I'm close to Earth. We usually don't question this biker is fully experimenting gravity: Source. But with the well-known "reduced gravity" ...
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### Why are tensions in the pulley different when the pulley has a mass or moment of inertia?

When two blocks are connected by a string passing over a pulley whose moment of inertia is given (means pulley is not massless) then why does the string not have same tensions?
3k views

### Conical train wheels

I've been reading about how the conical shape of train wheels helps trains round turns without a differential. For those who are unfamiliar with the idea, the conical shape allows the wheels to shift ...
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### Spring balance: what will be the reading? [duplicate]

There are two cases: When the two forces say L (for left) and R (for right) are equal. F=L=R What will be the reading? I know the reading would be F but why? When the two forces are unequal that ...
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### Is there a general rule for determining the direction of tension force?

Tension, for me, is a tricky thing. After finishing a related chapter of my book and watching a video, I still can't get a hang of it. Here is a situation: My knowledge is that tension, just like ...
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### A confusion regarding friction

Suppose there is a block which is being pulled by two forces A,B in opposite direction(as shown in figure). If we have no information regarding the forces $A$ and $B$, can we tell whether there is any ...
391 views

### Tension in a rope

In an ideal case, we assume strings and ropes to be massless and having same tension throughout. However, I was doing some questions which involved a rope with mass. The question was that if a ...