# What is Sum of forces: Definition and 27 Discussions

The Sum of All Fears is a political thriller novel, written by Tom Clancy and released on August 14, 1991. Serving as the sequel to Clear and Present Danger (1989), main character Jack Ryan, who is now the Deputy Director of Central Intelligence, tries to stop a crisis concerning the Middle East peace process where Palestinian and former East German terrorists conspire to bring the United States and Soviet Union into nuclear war. It debuted at number one on the New York Times bestseller list. A film adaptation, which is a reboot of the Jack Ryan film series and starring Ben Affleck as the younger iteration of the CIA analyst, was released on May 31, 2002.

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1. ### Wheel moving in rotation and translation

Hi :) 1/ First case A wheel with a mass ##m## and a radius ##r## moves in horizontal translation and rotates around itself. The wheel is just above the ground, doesn't touch it. The wheel rotates CW if the wheel moves in translation to the right. The ground is horizontal and there is no...
2. ### Not sure if I have the correct angle and mass for this sum of forces

Balance the forces east-west: 3.5kg*sin45º + 4.2kg*cos30º - 4.8kg*sin30º - E*cosΘ = 0 E*cosΘ = 3.712 kg balance north-south: 2.8kg + 3.5kg*cos45º - 4.2kg*sin30º - 4.8kg*cos30º + E*sinΘ = 0 E*sinΘ = 0.982 EsinΘ / EcosΘ = 0.982 / 3.712 tanΘ = 0.2645 Θ = 14.8º ◄ E = 3.712kg / cos14.8º = 3.84...
3. ### Confusion about Newton's laws, sum of forces equals zero

I've lately began working with Newtons laws problems at school again, and I've already ran into a few problems. When making calculations and solving problems, it is often nessecary to understand when forces are equal to zero, and when they are not. Since every force has an equal and opposite...
4. ### What is the solution to the Kinematics of Particles Homework?

Homework Statement Refer to figure please. Homework Equations ∑Fy=0 before string is cut The Attempt at a Solution I tried summing the two forces in the y direction before the strings were cut which would be the two tensions at a sin40° and minus the weight of the ball(mg). That gave me T in...
5. ### Calculate the forces and the work

Homework Statement A wheel moves to the rigth and rotates like a wheel of a bike. There are 2 bodies: - the wheel (red circle) + 2 red walls - the black arm The ground is fixed. The black arm can rotate around the red axis. The red axis is fixed to the wheel. There is no friction. The...
6. ### Understanding solution method for finding accelerations in a mechanical linkage

Homework Statement I was checking my work and Chegg uses the equations differently. Can somebody tell me why? Maybe I'm misunderstanding how/why to use the equation I chose. Homework Equations They say aB = -ω2ABRB/Ai I used aB = aA + αk x r - ω2rB/A The Attempt at a Solution So obviously...
7. ### Sum of Translational and Angular Forces

Hello, I'm trying to figure out the free body diagrams for the inverted pendulum problem and I'm having trouble figuring out the one equation: ##Psin\theta + Ncos\theta - mgsin\theta = ml\ddot{\theta} + m\ddot{x}cos\theta## I've never really seen a mixed sum of forces equation before where some...
8. ### Why do I have to make gravity positive to make this work?

Homework Statement Two objects are connected by a light string that passes over a frictionless pulley as shown in the figure below. m1 = 7.10 kg, m2 = 7.10 kg, and ϕ = 56°. When released from rest, m1 accelerates downward at 0.972 m/s2. For this to happen, the coefficient of kinetic friction...
9. ### Easy statics problem -- Block being hoisted by a pulley and rope

I drew a FBD about point A and came up with the two equations: ∑Fx=0 20sinθ - T-ab(cos70)=0 ΣFy =0 -20cosθ + T-ab(sin70) -20=0 My answer is not coming out so I either messed up on the FBD or the equations, some help would be appreciated. I'm on 3-10 by the way.
10. ### Hydrogen bonding force problem

Homework Statement In a DNA molecule, the base pair adenine and thymine is held together by two hydrogen bonds (see figure below). Let's model one of these hydrogen bonds as four point charges arranged along a straight line. Using the information in the figure below, calculate the...
11. ### Finding potential U from sum of forces F

< Mentor Note -- Thread moved to Homework Help from technical Physics forum > Hi, I had an exam and I had this question: A force acts on a particle of mass m, and its components are: Fx = 2axy + by2 + 6cz Fy = ax2 + 2byx Fz = 6cx a) Does this force is conservative? Show your calculations...
12. ### Find Forces on Hand and Arm Holding a Ball

Homework Statement When an object is static (not moving), forces and moments must balance to zero. A moment here is defined as the force applied to an object multiplied by the distance from the point of rotation (torque). A simple way of thinking about moment balances is to consider a seesaw...
13. ### Conservation of mechanical energy vs sum of forces

When do one use the principle of conservation of mechanical energy to find the velocity of a mass, and when would you use the sum of forces equals to the mass times acceleration, and there after use a ds=v dv in order to find the velocity. The specific question related to this is a spring fixed...
14. ### No, this is not correct. See my previous post.

Homework Statement A truck (1200kg) is traveling south at 22m/s a) what is the net force required to bring the truck to a stop in 330m? b) what is the cause of this net force? (im assuming the answer is friction due to brakes) Mass= 1200kg (1.2*10^4) Velocity= 22m/s [south] What force is...
15. ### Newton's second law with vectors

Homework Statement A 9 kg object is subjected to two forces, http://www.webassign.net/images/Farrowbolditalic.gif1 = 7 N i - 4 N j and [PLAIN][PLAIN]http://www.webassign.net/images/Farrowbolditalic.gif2 = 7 N i - 9 N j. The object is at rest at the origin at time t = 0. (a) What is the...
16. ### How do I find the acceleration in Newton's 3 Laws Problem?

Homework Statement The 20.0 kg box is being pushed with a 45.0N Force acting at an angle of 25.0*. The coefficient of kinetic friction on this surface is 0.150. Find the acceleration Homework Equations F=ma Fy=0 Fx=0 The Attempt at a Solution So I attempted this so far (sum)Fy=0 Py+Fn-Fg=0...
17. ### Vector Sum of Forces Experiment

Homework Statement http://cgscomwww.catlin.edu/sauerb/AP12/AP12_Labs/AP12_Lab_4_Forces_files/image002.jpg My experiment is like this picture found in the net. The weight in the middle is called R in my experiment, while the left one is P and the right Q. Now there is one question asked, the...
18. ### Sum of forces, vacuum and gravity

It's a theoretical study. I would like to understand how the sum of forces can be at 0 if I put an object (vacuum in it) in a big liquid disk (disk is fulled with liquid), the disk is big enough for agglomerate liquid (like this works with a planet, matter is agglomarate with gravity). There is...
19. ### Ladder problem, sum of forces and sum of torque

Homework Statement Hello, My homework is online it would be to much trouble for me to type it all out it has a diagram with it. I cannot copy and paste it either. So if someone would be so kind as to message me I can send it through email as a word doc with a screen shot attached. I have...
20. ### Block on a ramp Sum of forces, normal force, static friction, etc Question

Ok so I already know how to solve it by looking at an example my teacher did in class... This is what I did... 4. A 2.00 kg block is held in equilibrium on an incline of angle θ = 70° by a horizontal force vector F applied in the direction shown in the figure below. If the coefficient of static...
21. ### The total sum of forces in circular motion in gravitational field

Hello, I am now studying centripetal force. and the problem is that centripetal force in gravitational field. Let's talk about Ferris-wheel ride, this ride has some rooms to carry people and fixed to the edge of the wheel. Since it is rotating periodically, its magnitude of net force...
22. ### Simple sum of forces parachute problem

a 64 kg parachutist falling vertically at a speed of 6.3 m/s impacts the ground, which brings him to a complete stop in a distance of .92 m. assuming constant acceleration after his feet first touch, what is the average force exerted on the parachutist by the ground? i know: Vf=0 Vi=6.3...
23. ### A mass is attached to two strings, derive a formulas for sum of forces

Homework Statement Two wires are tied to the 300 g sphere shown in figure. The sphere revolves in a horizontal circle at a constant speed of 6.50 m/s. What is the tension in the upper wire?What is the tension in the lower wire? Write an equation for the sum of the forces along y. Use it to...
24. ### Sum of Forces in x- and y-directions

Homework Statement Yusef pushes a chair of mass m = 55.0 kg across a carpeted floor with a force F of magnitude F(push) = 144 N directed at theta = 35.0 degrees below the horizontal. The magnitude of the frictional force between the carpet and the floor is F(fr) = 106 N. What is the magnitude...
25. ### Equilibrium sum of forces question

Equilibrium question with distance and weight Homework Statement Would someone be able to tell me if my attempt at this is correct. It seems too easy. If it is not could you help? Homework Equations Sum of the forces in the X direction Sum of the forces in the Y direction Mid...
26. ### Solving MA: Sum of Forces = Mass x Acceleration

Homework Statement Homework Equations Sum of forces = MA The Attempt at a Solution I already found the answer to part A, which is 10kg. But for part B I am not sure which box to draw my FBD on.
27. ### Sum of forces does not equal zero

Hey, I was doing some statics problems involving friction for fun. I came across this one problem that concerned me greatly. The free body diagram looks something like what is posted. I know the picture is not great but I have the solution for this problem and I know the correct numbers, so you...