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. A

    Finding net force, acceleration and speed.

    A 150 kg motorcycle starts from rest and accelerates at a constant rate along a a distance of 350m. The applied force is 250 N and the coefficient of kinetic friction is 0.03 Find the net force applied to the motorcycle. Find the acceleration of the motorcycle. What is its speed at the...
  2. S

    Fluid flow around a sphere, what's the net force?

    Homework Statement A sphere of radius ##a## is submerged in a fluid which is flowing in the z-hat direction. There is some associated viscosity in the fluid which will exert a force on the sphere. Use symmetry to argue that the net force will be in the z-direction. Show that it will have the...
  3. T

    How Is the Net Gravity Force Calculated Between Earth, Moon, and a Rocket?

    Homework Statement The Earth has a mass of 5.98*1024 Kg and the moon has a mass of 7.35*1022 kg. The distance from the centre of the moon to the centre of the Earth is 3.84*108 m. A rocket with a total mass of 1200 kg is 3.0*108 m from the centre of the Earth and directly in between the Earth...
  4. N

    Net Force Dispute with Teacher

    1. A 1000 kg automobile initially moving 72 km/h jams the brakes and skids to a stop in a distance of 24 m on a dry pavement but stops in 81.6 m for a wet pavement. (Neglect reaction delay.) A. Calculate the applied forces for both weather conditions. B. What is the coefficient of friction for...
  5. H

    Finding Net Force [w/ Vector Addition]

    Homework Statement A 20 kg object is being acted on by a 90 N [E60N] force, a 40 N [S] force, and a 40 N [E27S] force. Find the net force acting on the object and its acceleration. Homework Equations ƩF = ma The Attempt at a Solution I understand that I have to add vector...
  6. PsychonautQQ

    Ferris Wheel work done by net force

    My textbook says that if you are on a ferris wheel that is rotating, the total work done by all the forces acting on your is zero. How is that possible? You are moving so isn't work being done to you?
  7. T

    Net Force of Charges on an Equilateral Triangle

    Homework Statement Three point charges have equal magnitudes, two being positive and one negative. These charges are fixed to the corners of an equilateral triangle. The magnitude of each of the charges is 2.9 µC. The lengths of the sides of the triangle are .02m Calculate the magnitude...
  8. T

    Electrostatics net force question

    Homework Statement I am having a problem with 8.4. I get an answer but it does not match the answer in the memo which I think is wrong. Homework Equations The Attempt at a Solution 8.1) T to P (Could someone explain why?) 8.2) Q = (3*10^-9)-(6*10^-9)/2 = -1.5*10^-9 (This is...
  9. H

    Nonzero net force involving no displacement. Is this accurate?

    So I am studying mechanical engineering, and I got into a debate with my (mit mechy) graduate roommate about the possibility of having a net nonzero force which involved no actual displacement of an object. Normally, when an object is accelerated along a direction (given an external force)...
  10. leviterande

    Will this propeller arrangement have a net force in one direction?

    Hi, I am very sorry if I have posted in the wrong forum, I don't know wether to post in classical physics or aerospace engineering. I have been wondering this theoretical thing a lot lately and I can't figure it out, it should have a simple straight answer though so your help is very...
  11. S

    Conservation of momentum and net force

    does anyone know why momentum is not conserved in this problem? I thought momentum was always conserved when no net force acted on the system? Is the ground considered the net force acting on the system? Even though it changes direction I was thinking momentum would still be conserved except...
  12. D

    The net force and centre of gravity of a one dimensional object

    I have been trying to derive a formula for the forces acting on and the centre of gravity of objects in a one dimensional space. I've started in one dimension to make things easier and intend to move on to two dimensions soon. I tried to do it without referring to any source and I got a solution...
  13. K

    Constant velocity and net force

    Homework Statement A man is pushing a 75 kg crate at constant velocity a distance of 12 m across a warehouse. He is pushing with a force of 225 N at an angle of 15° down from the horizontal. The coefficient of friction between the crate and the floor is 0.24. How much work did the man do...
  14. T

    Calculate the net force on square loop (Magnetism)

    Homework Statement A square loop of wire of side length L lies in the xy-plane, with its center at the origin and its sides parallel to the x- and y- axes. It carries a current i, in a counterclockwise direction, as viewed looking down the z-axis from the positive direction. The loop is in...
  15. R

    Net force on a charge - Coulomb's law

    Homework Statement What is the force F on the 1 nC charge at the bottom? Figure: http://session.masteringphysics.com/problemAsset/1384340/5/pic1.jpg Homework Equations Coulomb's law - k*qq/r^2 The Attempt at a Solution 1) After splitting up the net force into their respective...
  16. H

    Calculating the net force acting on a object from diagrams

    Homework Statement Calculate the net force acting on each object indicated in the following diagrams. (diagrams attached) Homework Equations Sine Law: sin a/a = sin b/b = sin c/ c Cosine Law: c^2 = a^2 + b^2 -2ab*cos(c) SOHCAHTOA The Attempt at a Solution a) c2 = a2 + b2 –...
  17. A

    Explain to me why the net force is found this way?

    Homework Statement Two crewmen pull a raft through a lock. One crewman pulls with a force of 130N Southwest at an angle of 34 degrees below the horizontal. The second crewman pulls at an angle of 45 degrees above the horizontal Northwest. With what force should the second crewman pull so that...
  18. A

    How Do Charges Affect Net Force Calculation?

    Homework Statement The drawing shows three point charges fixed in place. The charge at the coordinate origin has a? q1 = +8.50 µC; the other two have identical magnitudes, but opposite signs: q2 = -5.00 µC and q3 = +5.00 µC. http://img66.imageshack.us/my.php?image=p1818mv9.gif (a)...
  19. S

    Net force of two forces in a ring

    Homework Statement Consider the following ring: Considering that \theta = 30°, determine F1 and F2 in order for the net force to be oriented downards with magnitude 10^3 N and without any horizontal component. The Attempt at a Solution Alright, so, the problem is I find two conflicting...
  20. N

    What is the net force on a rocket and how is it calculated?

    Homework Statement I am trying to derive an equation for the net force, or thrust, acting upon a rocket. The equation I get is different from the standard equation given in most textbooks, so I want to know where I am going wrong.Homework Equations F = d(mv)/dt I also make use of the...
  21. R

    Calculating net force on four masses around a center mass?

    In the figure, a square of edge length 16.0 cm is formed by four spheres of masses m1 = 4.50 g, m2 = 2.80 g, m3 = 0.800 g, and m4 = 4.50 g. In unit-vector notation, what is the net gravitational force from them on a central sphere with mass m5 = 2.10 g? F = G (m1m2/r2) To get the...
  22. S

    Is there a net force as someone jumps?

    Homework Statement While someone is accelerating upwards but before the body leaves its feet, is there a net force? The person will eventually leave the ground. Homework Equations ƩFy = 0; or does ƩFy = ma? The Attempt at a Solution I pretty sure that the latter is true, this is so...
  23. S

    What is the reaction force to F(net) in Newton's 3rd law?

    Homework Statement A girl pulls her 4.00kg sled connected to a weightless rope. She pulls the rope on the sled and it goes faster and faster on a frictionless ice surface. The sled has an acceleration of 2.50m/s^2. What is the tension on the rope? What is the net force? Homework...
  24. Y

    Finding the Relationship Between Net Work and Change in Kinetic Energy

    Homework Statement First, let us consider a sled of mass m being pulled by a constant, horizontal force of magnitude F along a rough, horizontal surface. The sled is speeding up. Let us now consider the situation quantitatively. Let the mass of the sled be m and the magnitude of the net...
  25. S

    Net Force on a Descending Man Question

    Homework Statement 75.0kg Man decends from 3.1m above the ground. At 3.1m his feet touch the ground and he absorbs the landing through a constant acceleration of 0.6m to come to a verticle rest. What is the net force on him? Homework Equations Vi = √(2*a*y); a = -[(Vi)^2]/(-2*y); F =...
  26. P

    How exactly do you find the net force between charges?

    I was doing some homework problems, and I came across a couple I didn't know. I then realized I must have screwed up my understanding on electrical forces. For an electrical force, if there are two protons, the force is k*q1*q2/r^2. The direction is in the opposite direction. <---(+)...
  27. P

    Net Force Exerted by Two Charges on a Third Charge (Coulomb's Law)

    This problem has been posted before with different values for each variable and I did as best I could to complete it similarly. However, when I attempt to input my final answer I get it wrong every time. I just wanted to see where I am going wrong, thanks. Homework Statement Coulomb's law...
  28. J

    Finding net force using velocity graph?

    Finding net force using velocity graph? The figure(Figure 1) shows the velocity graph of a 2.5object as it moves along the x-axis. What is the net force acting on this object at t=7 ? The attempt at a solution Since F=ma, I tried first finding a by dividing 6 m by 7 s. Then I...
  29. P

    Calculating net force from a diagram

    Homework Statement Calculate the net force acting on each object indicated in the following diagrams. Homework Equations c^2 = a^2 + b^2 sinA/a = sinB/b = sinC/c c^2 = a^2 + b^2 - 2abcosC The Attempt at a Solution Fnet =? Fnet(v) = 8.0 N [N] + 10.0 N [S] = 10.0 N [S] - 8.0 N [N]...
  30. D

    Help finding the magnitude of the net force

    Three students converge on the last textbook in the store. All three grab it and begin to pull in the directions shown in the above figure. Student A exerts a force of 61.88 N, student B pulls with a force of 31.92 N, and student C pulls with a force of 104.20 N at an angle θ(theta)=80.8 degrees...
  31. B

    Sum of work = Work done by net force

    Suppose you have many forces acting on an object, and the object moves in space in some time interval. Each force has done some work on the object. Suppose you took all these values for work, added them up, (they are all scalars). You'd obtain a scalar equal to the net work done on the object...
  32. D

    Power problem, to use net force or work energy theorem?

    Homework Statement A helicopter, starting from rest, accelerates straight up from the roof of a hospital. The lifting force does work in raising the helicopter. An 720-kg helicopter rises from rest to a speed of 7.5 m/s in a time of 5.0 s. During this time it climbs to a height of 7.9 m...
  33. S

    What causes the normal force to increase in circular motion?

    Homework Statement In my physics book (Young and Freedman 12 edition), in the chapter about conservation of energy, it teaches me that I can use the theory of conservation of energy and discover the velocity at the bottom of a circular path, having the height of this circular path. I...
  34. S

    Physics Net Force Incline problem

    A 2.0 kg mass starts from rest and slides down an inclined plane 8.0 x 10^-1 m long in 0.50 sec. What net force is acting on the mass along the incline? Can someone please explain step by step in a descriptive way. I have a quiz tomorrow and I just can't even start this problem
  35. C

    Net Force on 2m Mass: Prove/Disprove?

    Homework Statement Three masses m, 2m and 3m are placed on a horizontal surface. A force F is shown acting on m3. Assuming μs,k is the same between all of the masses and the horizontal surface, answer the following: a) Find the expression for the net force on the 2m mass. b) For F constant...
  36. N

    What is the net force acting on an object at t=2 with a given momentum equation?

    Homework Statement An objects momentum is given by the following equation p(t) = 4t3-6t+1. What net force is acting on the objects at t=2?Homework Equations P=m*v F=Δp/ΔtThe Attempt at a Solution So, I was thinking if F=m*a I can change a and get F=m*(Δv/Δt) and knowing what I know about p...
  37. I

    Net force from a straight-line resultant?

    1.Two concurrent forces act on a box. The first force acts east at 13 Newtons and the second force acts west at 17 Newtons. What is the net force acting on the box? >Draw each vector using the tip to tail method. >Draw your resultant and label it "R" >With your ruler determine the...
  38. M

    Net force on 3 parallel wires carrying current.

    Homework Statement You are given 3 wires parallel to each other (1)------> I (2)<-------I (3)------->I http://www.webassign.net/knight/p32-38alt1.gif (not sure it this link works) I1=I2=I3 = 16A the distance between the wires is d=2cm length of the wires is l= 50cm Homework Equations I...
  39. I

    What Is the Net Force on the Middle Mass?

    Homework Statement Three masses (m1 = 4.4 kg, m2 = 13.2 kg and m3 = 8.8) hang from three identical springs in a motionless elevator. The springs all have the same spring constant, which is 268 N/m. The elevator is moving downward with a velocity of v = -3.7 m/s but accelerating downward at...
  40. T

    How to find the net force, acceleration, and speed of Hovercraft?

    A toy hovercraft has a mass of 914g. Each of the two fans pushes back on the air with a force of 0.38 N. a. If there's no friction acting on the hovercraft, what is the net force acting on it? b. What is the acceleration of the hovercraft? c. If you start with the hovercraft at rest, and...
  41. S

    Calculating Net Force for a Viper Accelerating at 45 km/hr in 2 seconds

    Homework Statement Dough boy took a ride in his new car, he hammers the throttle in 2 seconds and his velocity is 45 km/hr (assume constant acceleration). The mass of the Viper is approximately 800kg, Find the net force acting on the viper. To be honest I am clueless on this question, I have...
  42. C

    What Are the Components of Net Force for a Mass Swinging on a Rope?

    Homework Statement 2 kg mass swings on the end of a rope as shown in the figure below. At the highest point in the trajectory the string makes a 56 degree angle with respect to the horizontal and the tension on the string is 16.25 N. = (No Response) N Homework Equations So I know I need to...
  43. J

    Is the Net Force Zero in Constant Velocity and Other Physics Queries?

    Homework Statement Indicate whether the following statements are always true or can be false. (Select T-True, F-False. If the first is F and the rest T, enter FTTTTT). A) The net force which acts on an object which maintains a constant velocity is zero. B) If a net force acts on an...
  44. T

    Why Is My Calculation of the Net Force on q1 Incorrect?

    Homework Statement q1= 6.7 μC q2= -4.5 μC q3= 2.2 μC q4= 2.2 μC d= 7.7 cmWhat is the x-component of the net force on q1? Homework Equations The Attempt at a Solution This is part of an online problem set, and is currently the only question I have not answered correctly. I find it strange...
  45. J

    Net force, tension, acceleration, and magnitude

    Homework Statement Two blocks, of masses m1 = 10kg and m2 = 5kg respectively are connected by a massless unstretchable string and are pulled by an applied force Fa, up a frictionless incline which makes an angle of θ=30° with the horizontal. The tension in the string which connects the two...
  46. T

    Magnitude and direction of net force acting on a charge.

    Homework Statement Four charges, q1 = +195 µC, q2 = +60 µC, q3 = −145 µC, and q4 = +21 µC, are fixed at the corners of a 4 m by 5 m rectangle, as illustrated in the figure below. What are the magnitude and the direction of the net force acting on q1? (Assume the x-axis extends from q1 to...
  47. L

    Constant Velocity = positive net force? But how to write it?

    Homework Statement Lifting a 20lb bucket of sand a distance of 100 ft at a rate of 2ft/s. I would assume: [W=F*d] = [W = MA*d] = [W = M(v/t)*d] and at a constant velocity: rate of v/t=0 so [W = M(0)*d] = [W = 0*d] = [W = 0] However, a video online shows that you'd take 20lb*100 ft...
  48. S

    How can I find the net force of this ? (image included)

    Both arrows have the same angles http://imageshack.us/photo/my-images/337/drawingz.png/ How can I find the net force of this and the direction ? Thanks.
  49. P

    What is the net force on a cart that is pulled to the right with 100 pounds and to th

    1. What is the net force on a cart that is pulled to the right with 100 pounds and to the left with 30 pounds? Changes in motion are produced by a force or combination of forces. A force, in the simplest sense is a push or a pull. Its source may be gravitational, electrical, magnetic, or...
  50. A

    What is the net force in this question?

    Homework Statement I need to find the net force of the following, I am pretty sure i know the answer, but i just wanted to check to see if i am actually doing it correctly Homework Equations i just need to find the net force (i have attached the question) The Attempt at a Solution...
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