Net force Definition and 504 Threads

Net force is the vector sum of forces acting on a particle or body. The net force is a single force that replaces the effect of the original forces on the particle's motion. It gives the particle the same acceleration as all those actual forces together as described by Newton's second law of motion.
In physics, it is possible to determine the torque associated with the point of application of a net force so that it maintains the movement of jets of the object under the original system of forces. Its associated torque, the net force, becomes the resultant force and has the same effect on the rotational motion of the object as all actual forces taken together. It is possible for a system of forces to define a torque-free resultant force. In this case, the net force, when applied at the proper line of action, has the same effect on the body as all of the forces at their points of application. It is not always possible to find a torque-free resultant force.

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  1. J

    Help with Calculating Net Force, Resistance Forces and Work

    Hi all, I am having difficulty in understanding this basic phyics relating to force, work,and movement, and I am struggling to do these questions. I would appreciate any help. The following information was provided and then three questions followed. A boy drags a box by a rope across a level...
  2. F

    Answer: Calculate Net Force of Water on Dam of Width 'w' and Depth 'd

    Water stands at depth 'd' behind a dam of width 'w'. i. Find an expression for the net force of the water on the dam. ii. Evaluate the net force on a 100m high dam with a 60m water depth. Attempt For the first part: p=F/A A=wd pwd=F Then integrate from 0 to d which gives...
  3. A

    NET Force on Massless Body: Acceleration & Spring Force

    What happens when the NET force on a massless body is 0. I mean what will be the acceleration , if any? Also if we pull a massless spring, from one side with a force F1 and from the other side a force F2, what will be the spring force?
  4. S

    Find the magnitude of the net force acting on this object

    Homework Statement A 3.00 Kg object is moving in a plane, with its x and y coordinates given by x=5t^2-1 and y=3t^3+2, where x and y in meters and t in seconds. Find the magnitude of the net force acting on this object at t=2.00 secs. Homework Equations The Attempt at a Solution...
  5. N

    Motion along a line due to a constant net force

    Homework Statement In a cathode ray tube, electrons are accelerated from rest by a constant electric force of magnitude 6.4E-17 N during the first 2.0cm of the tubes length; then they move at essentially constant velocity another 45cm before hitting the screen. A) Find the speed of the...
  6. K

    Two point charges, Zero Net Force

    [SOLVED] Two point charges, Zero Net Force Homework Statement Two point charges of charge 7.40 μC and -1.80 μC are placed along the x-axis at x = 0.000 m and x = 0.300 m respectively. Where must a third charge, q, be placed along the x-axis so that it does not experience any net force because...
  7. C

    Net Force & Kinetic Energy: Does More Work Occur?

    Homework Statement The speed of a particle doubles and then doubles again because a net external force acts on it. Does the net force do more work during the first or the second doubling? Justify your answer. Homework Equations I'm not sure, but i think E = 1/2 mv(squared) The...
  8. L

    Impulse and Net Force Equations

    I have a problem in trying to express a net force equation for a falling elastic object when collision ensues. For instance, you drop a spring with a spring coefficient k. the spring compresses a distance x after a time t for a maximum time of tf and distance xf. the spring has a weight W...
  9. B

    Magnitude of buoyant and net force

    Homework Statement An emtpy rubber balloon has a mass of 0.0120 kg. The balloon is filled with helium at 0 degrees Celcius, 1 atm pressure, and a density of 0.179 kg / m3. The filled balloon has a radius of 0.500 m. A. What is the magnitude of the buoyant force acting on the balloon...
  10. M

    Calculating the Net Force of Bruce Nuclear Development

    Homework Statement The Bruce Nuclear Development is a CANDU style reactor. This means that it has a "vaccum building" to "suck" (the contents of a malfunction reactor to a safer place. Refer to the engineering "specs" for the needed information to calculate the net force of the atmposhere...
  11. I

    Net Force of object changing velocity

    [SOLVED] Net Force of object changing velocity Hi, I'm studying for a test, so there might be a few of these in the next hour or so. Homework Statement A supertanker of mass 1.0 X 10^{8} kg travels 3.5km, reaching a speed of 4.1km/h from rest. What was the magnitude of the unbalanced force...
  12. I

    Average net force acting on the performer if his mass is 65kg?

    [SOLVED] I really need help I understand the very simple questions and all, but when the book throws all these extra things at me, I get so lost. You might've remembered my earlier post (my first one), so I'm back with a bit more. If it takes a human cannonball 1.5s to exit a 1.6m long...
  13. P

    Net Force & Motion: A 9th Grader's Guide

    Homework Statement will a body necessarily remain at rest if the net force acting on it is zero?give a reason for ur answer...and I've just passed my ninth grade so if u cud please it to me explain at that level...:smile: Homework Equations The Attempt at a Solution
  14. T

    Finding the Coefficient of Kinetic Friction for a Sliding Baseball Player

    Forces/Friction I'm new, so I'd like to say thanks in advance for helping me. The site wants all answers to the 4th decimal place. Idk how stuff normally works around here, but a small explanation with the answer would help me understand this stuff better. 1. Three forces act on a particle...
  15. A

    Physics 11 Net force and Acceleration

    Homework Statement g=10m/s^2 A fully loaded Saturn rocket has a mass of 2.92x10^6kg. Its engines have a thrust of 3.34x10^7N. a) How much does the rocket weigh. answer 2.92x10^7 N b) What is the net force on the rocket when it blasts off? answer 4.2x10^6N c) What is the...
  16. L

    What is the net force acting on the truck?

    1. A man is lazily floating on an air mattress in a swimming pool. If the weight of the man and air mattress together is 740 N, what is the upward force of the water acting on the system of man and mattress? 2. A truck driving on a level highway is acted upon by the following forces: a...
  17. Saladsamurai

    Net Force of a charged particle (Coulomb's Law)

    Homework Statement I really can't see where I am going wrong here. I would latex out my work, but it would take way too long, so I have scanned it in. It should be easy enough to read though. Its NUMBER 7, fig 21-22 Also the blurr says '100 nC' The Attempt at a Solution
  18. J

    Rotating Electric Forces: How to Find X Values to Change Net Force Direction?

    Homework Statement Particles 2 and 4, of charge -e, are fixed in place on the y-axis at y2=-10.00 cm and y4=5.00cm. Particles 1 and 3, of charge -e, can be moved along the x axis. Particle 5 of charge +e is fixed at the origin. Initially particle 1 is at x1= -10.0cm and particle 3 is at x3=...
  19. N

    Where Should the Third Charge Be Placed for Equilibrium on the X-axis?

    Homework Statement Two point charges lie on the x-axis. A charge of +7.7 uC is at the origin, and a charge of -4.4 uC is at x = 10.0 cm. At what position x would a third charge q3 be in equilibrium? Homework Equations F = k(q1)(q2)/r^2 The Attempt at a Solution This was how I...
  20. T

    What Forces Act on a Tightrope Walker Falling into a Net?

    Homework Statement A 65 kilogram tightrope walker falls vertically downward with a velocity of 9.9m/s. She falls into a net which stretches 1.5m vertically as it breaks her fall. What is the average net force on the walker as her fall is being broken, and what is the G force that she...
  21. P

    Net Force Question with no velocity or time given.

    [SOLVED] Net Force Question with no velocity or time given. Homework Statement A ball of mass 0.6 kg flies through the air at low speed, so that air resistance is negligible. What is the net force acting on the ball while it is in motion? Homework Equations Fnet = m(change in...
  22. X

    What is the net force on an airplane window at an elevation of 12500 m?

    Homework Statement An airplane is flying at an elevation of 12500 m. The window on an airplane is a square of length 0.115 m on each side. What is the net force on the window? Homework Equations P = Po + pgh p = 1.26 kg/m^3 Pair = 101.3 kPa The Attempt at a Solution I thought...
  23. C

    What Is the Net Force Exerted on an Object?

    Hi, I would like to first open this post by saying that I am not a slacker, and I try my hardest to figure things out to the best of my abilities. I am in Physics 1 right now. We are studying what our book calls Forces in One Dimension. I have a problem, the problem being I have a...
  24. B

    Net Force & Acceleration of 6.20kg & 7.70kg Masses

    help, please :) Homework Statement Two masses are suspended by a string placed over a pulley supported by the ceiling (m1 = 2.20 kg and m2 = 7.70 kg) Consider up to be positive. What is the acceleration on the 6.20 kg mass? The net force? What is the acceleration on the 7.70 kg...
  25. F

    Solving Friction and Net Force Problems

    Help Me Please! You don't have to actually do this, but does anyone know how to so I can solve it myself? :confused::rolleyes: 1) A 50 Newton horizontal force is needed to keep an object weighing 500 Newtons moving at a constant velocity of 2.0 m/s across a horizontal surface. What is the...
  26. C

    Finding the Net Force on a Box on an Inclined Plane

    Homework Statement A box of mass, m, is on a plane inclined at an angle, q, relative to the horizontal. The coefficient of kinetic friction between the box and the incline is uk, and the body is accelerating down the incline. What is the net force on the body? The Attempt at a Solution...
  27. F

    Why the net force is only from external forces?

    We're learning about a systems center of mass and have: F_{net} = Ma_{com} But I having a problem understanding why the net force is only from external forces? Is it because internal forces follow Newtons third law so the net force from internal forces is 0? If that's the case then take...
  28. F

    Finding the Resultant Force of Three Vectors

    Consider 3 force vectors F1, F2, and F3. The vector F1 has magnitude F1 = 55N and direction θ = 41°; the vector F2 has magnitude F2 = 20N and direction θ = - 140°; and the vector F3 has magnitude F3 = 17N and direction θ = 140°. All the direction angles θ are measured from the positive x axis...
  29. B

    Net Force on a 1kg ball Rolling on a Banked Track

    A 1kg ball rolls along a circular track that is banked at 20 degrees. The normal force on the ball is 10.43N, tilted inward. The radius of the track is 10m. a. What is the net force on the ball (include direction)? b. How fast is the ball going for it to complete the turn? possible...
  30. O

    Solving Skiing Problems: Net Force, Speed & Free-Body Diagrams

    Homework Statement A skier goes down a slope with an angle of 35 degrees relative to the horizontal. Her mass, including all equipment, is 70 kg. The coefficient of kinetic friction between her skies and the snow is 0.15. A. Please draw a free-body diagram of the skier. B. Calculate the net...
  31. P

    What is the net force and power in a lawnmower system?

    [SOLVED] The NET FORCE and a lawnmower Homework Statement Well I am working on a question here and am finding trouble with one part. The answers are in brackets. The trouble I am having is with part c, where i believe you have to find the accleration then the time to work out power which is...
  32. S

    Distribution of weights and net force

    Can someone explain to me why putting different weights in certain angles can alter the force. I was just doing a lab in class using a force table, where the weights dangled and you have to prevent the ring from touching the pole in the center. If the mass of the object doesn't change and ( I'm...
  33. S

    Question about Terminal Velocity and Net Force

    My physics teacher told my class that in order for there to movement, there must be a net force on an object. He also said that when an object reaches terminal velocity the Fnet is zero because air resistance equals that of the object's weight. Then, he said that the object continues to fall...
  34. I

    Net Force of a Rocket and Acceleration

    Homework Statement An 8.0Kg rocket is fired and encounters a force of air resistance of 4.9N. If the rocket's engines applied 100N of thrust: A. What is the Net Force on the rocket? B. What is the Rocket's Acceleration? Homework Equations (A) F=MA (B) Is it (Vfinal - Vinitial)/T? The...
  35. S

    How Do You Calculate the Net Force and Its Magnitude on an Object?

    Homework Statement A crate is pulled to the right (positive x-axis) with a force of 82.0 N, to the left with a force of 115 N, upward with a force of 565 N, and downward with a force of 236 N. Find the magnitude and direction of the net force on the crate. ---> I'm a bit confused about net...
  36. P

    Net force given 40 degree angle, coef. of kinetic friction=.3, and mass=80kg

    Homework Statement angle is in relation to horizontal Homework Equations f net=m*a The Attempt at a Solution yikes! i don't know! i appreciate ANY help!
  37. B

    Find the Net Force on Ball A from Balls B & C

    Homework Statement Each ball weighs 3.00 kg A is 10cm from C to the left and B is 40cm to the right of A Homework Equations F=Gm1m2/r^2 The Attempt at a Solution ive tried adding the forces that each ball apply to A and subtracting it. i know each has its own force acting on A...
  38. M

    What force is needed to keep the box at rest on an inclined plane?

    Homework Statement (a) A box is placed on an frictionless inclined plane with an angle of 18° from the horizontal. The box has a mass of 35 kg, what is the magnitude of the acceleration of the box along the inclined plane? (b) What magnitude of force would you need to apply to the box in...
  39. T

    Calculating the Net Force Acting on a 2.75 kg Object

    Homework Statement A 2.75 kg object is moving in a plane, with its x and y coordinates given by x = 7t^2 - 4 and y = 5t^3 + 1, where x and y are in meters and t is in seconds. Find the magnitude of the net force acting on this object at t = 2.35 s. Homework Equations F=ma The...
  40. P

    How Do You Calculate the Net Force on a Ball in Flight?

    1. A ball is flying through the air, and at a given point in the flight, the ball is submitted to a gravitational force: F(g) = 1,5 N [downwards] and air resistance: F(air) = 0,50 N [32° above the horizontal]. Calculate the net force on the ball. 2. F (nette) = m x a 3. I thought I...
  41. S

    What does the area under a force vs. position curve represent?

    Homework Statement A small box is moved from position x1 to x2 by a net force which varies with position. On a graph, I plot the net force on the box vs. its position. The area in between the force curve and the x-axis is ...... And I am not sure if it is the work done on the box or may be...
  42. K

    What Misconceptions Exist About Net Force and Motion?

    The 'net force' in the statements below is the sum of ALL forces acting on the body. During the collision of a car with a locomotive, the locomotive exerts an equal size force on the car as the car exerts on the locomotive. False If an object's speed does not change, no net force is...
  43. E

    Calculating the Net Force on a Model Airplane

    Homework Statement A model airplane has a momentum given by [(0.25 kg . m/s^3)t^2 - (0.75 kg . m/s^2)t]\hat{i} a.) What are the x- , y- , and z- components of the net force on the airplane? b.) At what time t is the x-component of the net force on the airplane equal to zero? Homework...
  44. M

    Net force on ball from ground to top

    Homework Statement A ball is tossed up into the air. It reaches maximum height and comes back down. What is the net force on the ball at the following situations: a. The ball is moving upward as it is released. b. The ball is at it's highest point. (when it comes to a stop i suppose)...
  45. K

    What is the horizontal acceleration of a 7.00-kg block with two given forces?

    Homework Statement Two forces, F1 and F2, act on the 7.00-kg block shown in the drawing. The magnitudes of the forces are F1=65.9 N and F2=22.7 N. Take the positive direction to be to the right. Find the horizontal acceleration of the block, including sign...
  46. N

    Net Force on Charges in Equilateral Triangle System

    Homework Statement Three rigid rods are joined to form an equilateral triangle ABC of side 1m.Three particles carrying charge 1C are placed at the vertices.The whole system is in equilibrium in an inertial frame.What is the magnitude of the net force on each of the charges? Homework...
  47. E

    Net force an an infinitesimal string

    Homework Statement The book I am using (Zwiebach on page 66) uses the expression dF_v = T_0 \frac{ \partial{y}}{\partial{x}} |_{x+dx} -T_0 \frac{ \partial{y}}{\partial{x}} |_{x} for the force on an infinitesimal length of string. We assume dy/dx is much less than 1. I am not sure how the...
  48. E

    Net force an an infinitesimal string

    Homework Statement The book I am using (Zwiebach on page 66) uses the expression hello dF_v = T_0 \frac{ \partial{y}{\partial{x}} |_{x+dx} -T_0 \frac{ \partial{y}{\partial{x}} |_{x} Homework Equations The Attempt at a Solution Homework Statement Homework Equations The Attempt at a...
  49. I

    Net force exerted by two charges on a 3rd charge

    Homework Statement The drawing shows three point charges fixed in place. The charge at the coordinate origin has a value of q1 = +9.00 µC; the other two have identical magnitudes, but opposite signs: q2 = -5.00 µC and q3 = +5.00 µC. For the problem imagine the x-y coordinate grid with a +...
  50. X

    Find the vector of the net Force

    Take q1=25uC at (0,1), q2=20uC. at (2,0), and q3=? at (2,2). IF the force on q1 points in the -x direction, (a) what is q3 and (b) what is the magnitude of the force on q1? F=k(q1,q2)/r^2 coulombs law I know since q1 points in the -x direction that q3=q2. So (a)=20uC. I'm not sure...
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