What is Newtons laws of motion: Definition and 20 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.

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  1. D

    A box with the mass m = 25 kg is sliding up a hill

    What I have already attempted is on my Ipad and I don't know how to upload it on here. With hope of help DJ
  2. S

    Weight of gold chain when dropped on a weighing scale

    The force exerted downwards on the scale by the chain when it is kept on it would be Fg= Mg =λLg where λ is the linear mass density However when the chain is dropped onto the scale it exerts an additional force due to its change in momentum The force exerted by each part of the chain would...
  3. OlegKmechak

    Is there some geometrical interpretation of force from Newton's Laws?

    dP = F dt dE = F dr or if we introduce ds = (dt, dr) (dP, dE) = F ds And both dP and dE are constant in closed system. Some questions: - How does its implies on definition of Force? - Is there some clever geometrical interpretation of Force? - Why P and E seems almost interchengable?
  4. Hamiltonian

    Two block problems with friction

    the maximum value of friction between the surfaces of the blocks is ##60N## the friction should be self-adjusting until this maximum value. Hence the force of friction in the given scenario should be = 30N but this is physically impossible as if this is the case the top block will be at rest and...
  5. Hamiltonian

    Why Does the Friction Force Not Match in the Two Block Problem?

    when a force of 10N is applied to the 4kg block the force of friction between the two blocks will also equal 10N as the maximum value of friction between the two surfaces is f = N##\mu## = 20N. if you look at this free body diagram f = F = 10N so the net force acting on the top(4kg) block will...
  6. R

    Is Newton's Second Law Flawed? An Exploration of Zero Force in Space

    Newton's law's of motion have been used for hundred's of years, but the second law is wrong and here is why. Newton's second says that net force equals the mass of the object multiplied by the acceleration or F∑=MA. This is fairly simple and straight forward, but is easy to prove wrong. If we...
  7. Zeke Bevan

    Newton's Third Law Problem: Two masses, a rope and a pulley

    Homework Statement Two blocks are attached to opposite ends of a massless rope that goes over a massless, frictionless, stationary pulley. One of the blocks w/ a mass of 1.5 kg accelerates downward at (3/4)g. A. What is the mass of the other block? Homework Equations There were no given...
  8. DracoMalfoy

    Applying Newtons Laws: Incline, static friction, kid on sled

    Homework Statement [/B] A child sits on a sled (50kg) on a snowy hill with an incline of 5 degrees. The coefficient of static friction is 0.05. What downward force must a parent apply parallel to the normal force, to prevent the child from sliding down the hill? (Answer: 366N)Homework Equations...
  9. T

    Deriving motion equations for two blocks on a rough table

    Two small blocks, each of mass m, are connected by a string of constant length 4h and negligible mass. Block A is placed on a very rough tabletop as shown below, and block B hangs over the edge of the table. The tabletop is a distance 2h above the floor. Block A is then released from rest at a...
  10. T

    What is the Correct Equation for Accurate Accident Reconstruction?

    Hi, my name is Tom, I've been struggling with a real world problem. I hoping that someone can guide me to the formula that will help with a real world speed question. I was in an accident, an accident that could happen to any one. I know that one of the equations in the accident reconstruction...
  11. V

    Newton's laws of motion -- finding the velocity of a Block in a pulley system

    Homework Statement Determine the speed with which block B rises in figures if the end of cord at A is pulled down with a speed of 2ms^-1 Homework Equations Given Velocity downwards at A=2m/s The Attempt at a Solution Really stuck... Couldn't even start the question solving...I know all...
  12. T

    Gravitation force of a disk with a hole

    Homework Statement [/B]Hello, I have derived the equation for the gravitational force for a disk to be 2Ggm/a^2(1-x/sqrt(a^2 - x^2) when an object is added on top of the system. My question is would the force still be somewhat similar if the disk now had a small hollow of radius c...
  13. S

    Is a Vertically Hung Spring Mass System SHM?

    In an SHM, the only force that should be acting, that is the net force should be the restoring force F, by definition... F = -kx For example there is a massless spring of spring constant k attached to the ceiling and there is a body of mass m hung at it and avoiding all kinds of friction...
  14. L

    Astrophysicists and their use of physics in their studies?

    I am writing a paragraph on astrophysicists. I want to incorporate a connection between the physics that we are learning and an astrophysicist's use of the same principles in their studies. Unfortunately, there is not much information about this on the internet. What I have found is that...
  15. M

    Newton's Law System With Both Frictions

    Homework Statement Find the minimum mass that is needed to get the system moving and the acceleration of the system once it starts to move. The coefficient of static friction between the mass and the table is 0.54 and the kinetic friction coefficient is 0.3. Homework Equations...
  16. MARK 42

    No problem, glad I could help!

    In the arrangement shown in the figure, find the acceleration of M in upward direction. The pulleys are light. The strings are mass less and friction between the string and the pulleys is negligible. The options are given. The final answer is (B) and this was the solution: I don't...
  17. Prashant91

    Scale Reading in Elevator: Mass, Acceleration, and Velocity Calculations

    Homework Statement A person stands on a scale in a elevator at rest. The scale reads 900N. 1) what is the persons mass 2) the elevator accelerates up at 2.5m/s^2. What does the scale read now ? 3)The elevator then continues to move upwards with a steady speed of 4m/s for 5 seconds. What does...
  18. T

    Bernoullis from the laws of motion

    I am trying to understand Bernoullis from Newton laws applied to molecular dynamics (as opposed to conservation laws) From the conservation laws I understand for a incompressible invicous (experiencing no friction effects ) Ideal fluid Mass is neither created nor destroyed Mass in = Mass...
  19. S

    Circular Motion and Gravitation of tether ball

    Homework Statement There is a tether ball swinging around in a uniform circle on a rope that is 1.90m long. Marcus hit the ball so hard that the string holding the ball made a 20.0 degree angle to the horizontal. What is the tension in the rope if the ball has a mass of 1.40 kg? Assume that the...
  20. GiantSheeps

    How Is Impulse Calculated in Baseball Physics?

    Homework Statement A(n) 0.142 kg baseball is thrown with a speed of 19.5 m/s. It is hit straight back at the pitcher with a final speed of 26.6 m/s. What is the magnitude of the impulse delivered to the ball? Answer in units of kg · m/s (part 2) Find the average force exerted by the bat...