What is Newton's second law: Definition and 264 Discussions

In classical mechanics, Newton's laws of motion are three laws that describe the relationship between the motion of an object and the forces acting on it. The first law states that an object either remains at rest or continues to move at a constant velocity, unless it is acted upon by an external force. The second law states that the rate of change of momentum of an object is directly proportional to the force applied, or, for an object with constant mass, that the net force on an object is equal to the mass of that object multiplied by the acceleration. The third law states that when one object exerts a force on a second object, that second object exerts a force that is equal in magnitude and opposite in direction on the first object.
The three laws of motion were first compiled by Isaac Newton in his Philosophiæ Naturalis Principia Mathematica (Mathematical Principles of Natural Philosophy), first published in 1687. Newton used them to explain and investigate the motion of many physical objects and systems, which laid the foundation for Newtonian mechanics.

View More On Wikipedia.org
Recent contents Top users
  1. P

    Can Newton's Second Law be absolutely proven mathematically?

    So if you've seen/posted in any of my other threads you probably noticed that I've been trying to figure out how the modern form of Newton's Second Law (\textit{F = ma} or \textit{F = m}\frac{dv}{dt}) came to be formulated. After reading many different websites and sources, I think I've...
  2. E

    Mass vs. Acceleration Graph Proving Newton's Second Law

    Homework Statement Okay, so here's the question: Does your plot of acceleration versus hanging mass verify the Second Law? Explain your answer. The experiment involved a cart with weights and a hanging mass on the edge of a table. After each trial, one weight was removed from the cart...
  3. N

    Newton's second law clarification - derivative, constant mass

    Newton's second law states F = d(mv)/dt as this law is valid only for constant mass systems it is also written as F = md(v)/dt. But let's suppose the mass was not a constant, then the derivative of the law would become F = m'v + mv' (where by ' I mean derivative, m' = dm/dt), would that be...
  4. S

    Newton's second law of motion

    Homework Statement http://img104.herosh.com/2011/05/20/237027318.jpg Homework Equations F=ma The Attempt at a Solution i got 8.66x10^-17 and 3.9x10^-67 Please i need help.
  5. J

    Which formulation of Newton's second law is more fundamental?

    Which formulation of Newton's second law is more fundamental?? Hi there! I was Googling for interesting demonstrations in Physics, and I was lucky enough to find very interesting blog. Although it is completely new- the guy is writing it only for two weeks, but it already has a lot of nice...
  6. D

    Newton's Second Law Incline (constant accel)

    Newton's Second Law...Incline (constant accel) Homework Statement Given: mass of block of 5.0 kg incline angle is 37theta coeff kinetic friction is 0.50 What is the force, directed up the inline, required to move the block at constant speed up the incline? The...
  7. I

    Calculating Velocity of a Falling Water Drop Using Newton's Second Law

    Homework Statement A drop of water of mass m is falling vertically towards the ground. Due to moisture, the mass of the drop is increasing as given by m=kt2. The equation of motion is mdv/dt + vdm/dt = mg find v after 1 second.Homework Equations The integrating factor of an imperfect...
  8. H

    Is Newton's second law somewhat arbitrary

    Is Newton's second law somewhat "arbitrary" I am trying to undestand something basic here. Newton formulated his second law as: The rate of change of momentum of an object equals the force acting on it in (considering througout this discussion only intertial frames to keep things simple)...
  9. T

    Newton's second law and rounding a corner

    Does Newton‘s second law hold true for an observer in a car as it speeds up, slows down or rounds a corner?
  10. E

    Deriving Motion Equation from Newton's Second Law

    Homework Statement An object is dropped from a height above a pool of water. Start with Newton’s 2nd law, F = ma and use the general expression for acceleration, ay=d2y/dt2 to generate a differential equation Homework Equations F=ma -mg=m d2y/dt2 The Attempt at a Solution We had this...
  11. P

    Newton's Second Law: Combined Masses

    A block sits on a horizontal frictionless table. A thread attached to its runs horizontally to a pulley at the edge of the table, passes over the pulley and supports a load of 1.0 kg. The size of the acceleration of both the block and the load is 2.0 m/s. Find the tension in the thread: To...
  12. P

    Newton's Second Law and an elevator

    So I had this problem regarding an elevator with a man inside. In the first part of the question we had to calculate the tension in the cable, which I managed to do alright. The Second Part however, I am having difficulty and it asks for the following: When the lift is decelerating by 1...
  13. M

    Newton's Second Law - Friction

    Homework Statement Two masses, m1 = 3.50kg and m2 = 5.00 kg, are on a frictionless tabletop and mass m3 = 7.60kg is hanging from m1. THE COEFFICIENT OF STATIC AND KINETIC FRICTION BETWEEN m1 AND m2 are 0.60 and 0.50 respectively. a) What are the acceleration of m1 and m2? Homework Equations...
  14. K

    Newton's Second law: Help, please?

    Homework Statement Boxes A and B are at rest on a conveyor belt that is initially at rest. The belt is suddenly started in an upward direction so that slipping occurs between the belt and the boxes. Knowing that the coefficients of kinetic friction between the belt and the boxes are (\muk)A =...
  15. D

    Rocket launching - Newton's Second Law

    Homework Statement Suppose that during the launch of a rocket from the surface of the earth, an astronaut onboard the rocket stands on a bathroom scale and measures her weight to be 3.6 times her normal weight. Determine the acceleration of the rocket. Homework Equations Fnet \sumF = ma or...
  16. R

    Newton's Second Law Elevator Problem

    A student stands on a bathroom scale in an elevator at rest on the 64th floor of a building. The scale reads 836 N. (a) As the elevator moves up, the scale reading increases to 936 N, then decreases back to 836 N. Find the acceleration of the elevator (ms^-2). (b) As the elevator approaches...
  17. J

    Newton's Second Law of Motion: F=ma, Compute v^2

    Newton's Second law of motion F=ma, where m is the mass of the object that undergoes an acceleration a due to to an applied force F. This law is accurate at low speeds. At high speeds, we use the corresponding formula from Einstein's theory of relativity...
  18. A

    Newton's Second Law: (Major Flaw in Lab)

    Homework Statement 2. Question 3 The Attempt at a Solution I would like to state the fact that friction during the lab was not taken account of however I do not understand how that ties into question number three... Is it because the graph is based on a theoretical value which is...
  19. P

    Forces, Newton's Second Law

    Forces of 10.6 N north, 20.8 N east, and 14.3 N south are simultaneously applied to a 3.76 kg mass as it rests on an air table. What is the magnitude of its acceleration? I tried F=√(10.6²+20.8²) a=F/m ..however this is incorrect. Can someone please tell me where I am going wrong?
  20. JJBladester

    Newton's Second Law vs. Energy Equations

    Homework Statement I'm taking a test next week on kinetics and energy of moving particles. Problems include things like sliding blocks, friction, braking automobiles, collars sliding on poles, springs, max/min heights/velocities, tensions, accelerations, etc... We learned two ways of...
  21. A

    Deriving Newton's 2nd Law for Single Body in 1D Case

    Homework Statement How can Newton's 2nd law be derived for a single body in an 1Dimesional case ? Homework Equations F=m(du/dt) The Attempt at a Solution It is given that the principle of conservation of energy must be used,for the derivation. Are there any more hints?
  22. M

    Pulling a box up a ramp - Newton's second law

    Homework Statement A box is being pulled up a ramp with a force F. The ramp has a 30 degree incline with the horizontal. write the sum of the forces in the x direction and y direction. Make the x and y coordinate system be parallel and perpendicular with the ramp. The Attempt at a...
  23. B

    Oscillations Spring constant Newton's second law

    So i have the equation m*(d2x/dt^2)+c*(dx/dt)+kx=0, where d2x/dt^2 is the second derivative. So I'm given that m=10 kg, and k=28 N/m. At time t=0 the mass is displaced to x=.18m and then released from rest. I need to derive an expression for the displacement x and the velocity v of the...
  24. R

    Finding Spring Stiffness and Effective Mass for Suspended Beam

    Homework Statement A cable is used to suspend a 400 kg safe. It is being lowered at 6 m/s, when it stops suddenly. Find the maximum dynamic tension and the frequency of vibration. k=2(105 N/m Homework Equations Newton's 2nd law The Attempt at a Solution Well I easily found the...
  25. S

    How Do You Calculate the Mass of a Trailer Using Newton's Second Law?

    Homework Statement A car pulls a trailer along a level road at a steady speed of 10 m/s and the pull on the trailer is 100N. When the car accelerates at 0.5 m/s2 the pull on the trailer is 150N. Assuming the resistance to motion to be constant, find the mass of the trailer. Homework...
  26. S

    Newton's Second Law Particle Problem

    Homework Statement 4. A particle of mass m is experiences a Force that attracts the particle following F(x) = -k*x^-2 (an inverse square relationship) where x is the distance from an origin at x = 0 and k is a positive constant. If the particle is released from rest at x = d, how long...
  27. S

    Newton's second law to find mass

    Homework Statement the rotor blades of a helicopter propel 2500 kg of air vertically downwards every second. The air, initially at rest, is accelerated to a speed of 15 ms-1. If the helicopter starts to rise with an acceleration of 12.5 ms-2, the mass of the helicopter is... a. 1680 kg...
  28. A

    Relativistic form of Newton's second law

    SOLVED (Problem 10, Chapter 2, Modern Physics - Serway) Homework Statement Recall that the magnetic force on a charge q moving with velocity \vec{v} in a magnetic field \vec{B} is equal to q\vec{v}\times\vec{B}. If a charged particle moves in a circular orbit with a fixed speed v in the...
  29. S

    Newton's second law with linear and angular momentum

    If a force is applied to an object, will the object always experience the same linear momentum change regardless of where the force is applied, or will applying the force away from the objects centre of mass cause lesser linear momentum to develop but with the addition of angular momentum...
  30. D

    Newton's Second Law for a Single Force

    Homework Statement Stopping a Salmon The tension at which a fishing line snaps is commonly called the line's "strength." What minimum strength is needed for a line that is to stop a salmon of weight 85 N in 11.6 cm if the fish is initially drifting at 3.0 m/s? Assume a constant acceleration...
  31. S

    Assignment help needed. (banked curves, Newton's second law)

    I was solving my assignment questions, and found two questions particularly challenging. So I post this thread to get some helps. 1. Homework Statement Question 1. Astronauts have connected a line between their 3500kg space tug and a 6200 kg asteroid. Using their ship's engine, they pull on...
  32. A

    Newton's Second Law and Friction

    Homework Statement Block A weighs 1.14 and block B weighs 3.66. Block A rests on top of block B and has a cable connecting it to the wall on its right. The coefficient of kinetic friction between all surfaces is 0.300. Find the magnitude of the horizontal force necessary to drag block B to...
  33. N

    Newton's second law and direction of force

    Homework Statement A particle is traveling in a straight line at a constant speed of 22.1 m/s. Suddenly, a constant force of 12.6 N acts on it, bringing it to a stop in a distance of 55.3 m. Homework Equations The Attempt at a Solution (a) What is the direction of the force...
  34. S

    W=Fd, Work & Newton's Second Law problem

    [SOLVED] W=Fd, Work & Newton's Second Law problem Homework Statement a) Find the force to give a helicopter of mass M an acceleration of 0.10g upward b) Find the work done by this force as the helicopter moves a distance of h upward. Homework Equations W=F_{net}d F=ma The Attempt...
  35. C

    Is conservation laws are more fundamental than Newton's second law?

    Is conservation laws are more fundamental than Newton's second law in Newtonian mechanics? I know from the point of view of Noether's theorem conservation laws are more fundamental. But all the conservation laws can be derived from the F= ma equation. And from these conservation laws I can't...
  36. M

    Relativistic version of Newton's second law with parallel force

    Homework Statement "Given F=dp/dt. If the force is parallel to velocity show that F=γ3ma." Homework Equations F=dp/dt and p=γmv The Attempt at a Solution Since the force is the first derivative of the momentum with respect to time, and γ and v both vary with time since there is a...
  37. P

    Calculating Net Force from Acceleration and Distance: A Problem Solving Approach

    When a 53.4g tennis ball is served, it accelerates from rest to a speed of 40.5m/s. The impact with the racket gives the ball a constant acceleration over a distancce of 46.6cm. What is the mgnitude of the net force acting on the ball? I converted the 53.5g into kg=.0535kg I converted 46.6cm...
  38. W

    Newton's second law problem;

    Newton's second law problem; Please Help! Block M = 7.50 kg is initially moving up the incline and is increasing speed with a = 4.35 m/s2. The applied force F is horizontal. The coefficients of friction between the block and incline are fs = 0:443 and fk = 0:312. The angle of the incline is...
  39. F

    What is the tension in the cord holding a suspended sphere at a 23° angle?

    Homework Statement A sphere of mass 1.1 × 10^-4 kg is suspended from a cord. A steady horizontal breeze pushes the sphere so that the cord makes a constant angle of 23° with the vertical. Find (a) the magnitude of that push and (b) the tension in the cord. Homework Equations F_g = m*g F_net...
  40. M

    How Do Magnets Propel the Superman Ride at Magic Mountain?

    In the amusement park ride known as Magic Mountain Superman, powerful magnets accelerate a car and its riders from rest to 42 m/s (around 90 mi/h) in a time of 8.1 s. The mass of the car and riders is 4800 kg. Find the average net force exerted on the car and riders by the magnets. my...
  41. Z

    Use Newton's second law to find the net force acting on both blocks

    Homework Statement Two blocks with masses m1 = 1.10 kg and m2 = 3.20 kg are connected by a massless string. They are released from rest. The coefficient of kinetic friction between the upper block and the surface is 0.490. Assume that the pulley has a negligible mass and is frictionless, and...
  42. O

    Solve Newton's Second Law: Find Angle of Elevation w/ 1.86cm Blocks

    Homework Statement Two calibrated elevation blocks have a combined thickness of 1.86 cm. Find the angle of elevation of the 1.00-m long track for this situation. Homework Equations F = ma? The Attempt at a Solution I'm having a LOT of trouble, even beginning to draw the picture for...
  43. A

    4-9 Force/mass - Newton's Second Law question

    Homework Statement When a horizontal force F is applied to a box having a mass m, the box sides on a level floor, opposed by a force of kinetic friction f. a. What magnitude of acceleration occurs for the box? b. Calculate the acceleration if the horizontal force is 412N, friction is...
  44. I

    Verifying the Limits of Newton's Second Law with Blocks

    Homework Statement Imagine that there is a slab (call it block 1) on top of which sits a block (call it block 2). The slab connects to a cable that passed through a pulley and attaches to another block (call it block 3), hanging freely. Assuming that the coefficient of kinetic friction is...
  45. S

    Newton's Second Law and Tension - very confused

    This is not a homework problem so I am ignoring the template. I was watching Walter Lewin's video lectures and this experiment he performs intrigues me. I have given it a thought for over an hour but have no answer as to which and why will that string break. I have uploaded the experiment...
  46. K

    Newton's Second Law: Acceleration & Mass Relationship

    According to Newton's second law, how are acceleration and mass related? Directly or indirectly when force is constant? I believe it indirectly. Am I right?
  47. M

    Question Newton's second Law: F= M * A

    Hi! Why is a in F=m*a equal to a =(d^2 x) / (d t )^2 and not to (d x)^2 / (d t )^2 Mark
  48. D

    Newton's second law cosine and sine

    Newton's second law is taking my mind for a spin and for some reason had me contemplating how it works for several hours. This is all with respect to an incline and an object sitting on the incline with no friction. If the problem does not give you the mass of the object can you completely...
  49. S

    The d in Newton's second law of motion?

    the "d" in Newton's second law of motion? Hello there my fellow quantum inquisitors. I was just over in the physics forums library and was wondering what the "d" in the equations of Newton's second law of motion means? Thanks in Advance, ScienceNerd36.
  50. D

    Newton's second law problem

    Homework Statement A triangle shaped moving block of mass M2 is pushed by force F , a block of mass M1 is on the other block, a)what should be the F force so that the block will be in rest relative to M2? b)what should be the Acceleration of M1 so that the block M2 will move up on the block...
Back
Top