What is Newtons law: Definition and 97 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. Hamiltonian

    Verifying that Newton's Equations are equivalent to the EL equations

    In the past, I have shown relatively easily that if we have a lagrangian of the form ##\mathcal{L}=\frac{1}{2}\dot{\mathbf{q}}^2-V(\mathbf{q})## simply plugging this into the EL equation gives us newtons second law: ##\ddot{\mathbf{q}}=-\frac{\partial V}{\partial \mathbf{q}}##. I am unfamiliar...
  2. thomas_shvekher

    Newton's Third Law: Action and Reaction Explained

  3. D

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

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  4. D

    A dial can spin on a fixed rotational axis

    What I have done is on my Ipad that I cant upload or at least don't know how to... :/ With hope of help DJ
  5. Adesh

    Analysis of a deformable body and Newton's 3rd Law

    I'm posting the images of "Sommerfeld's Lectures on Theoretical Physics, Vol 2, Mechanics of Deformable Bodies" I apologize for posting the images rather than writing out the whole thing. But I did it to so that nothing should be missed, as writing out the...
  6. D

    Freefall v Jetpack: Will He/She Stay Afloat or Crash?

    Homework Statement There is a random person falling from the sky. He remembers that he has a jetpack. Unfortunately, his jetpack is weak and is only able to provide upward force equivalent to Fg. WILL HE?SHE STAY AFLOAT OR WILL HE?SHE CRASH INTO THE GROUND? What acceleration will he/she hit...
  7. D

    Free Fall vs Jetpack: Will He/She Stay Afloat?

    There is a random person falling from the sky. He remembers that he has a jetpack. Unfortunately, his jetpack is weak and is only able to provide upward force equivalent to Fg. WILL HE?SHE STAY AFLOAT OR WILL HE?SHE CRASH INTO THE GROUND? What acceleration will he/she hit the ground?
  8. parshyaa

    Question about inertial and non inertial frames

    Suppose a person A is standing in a bus and bus is accelerating forward then when a person B standing outside observes A he see that A is accelerating in forward direction then there must be a force acting on him which is making him accelarating(because Newtons first law holds in Earth's frame)...
  9. parshyaa

    A few questions related to tension in a string

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  10. K

    Analysis of tennis string tension

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  11. A

    Sphere rolling with slipping on a movable platform

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  12. alexandria

    Investigating Net Force in Two Dimensions

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  13. Frankenstein19

    Apparent weight loss 2nd Newtons Law elevator problem

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  14. B

    Net Force on 5.32 x 10^4 kg Airplane: Solve the Mystery

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  15. sidt36

    Mastering Newton's Laws for 9th Grade Talent Exam: Overcoming FBD Problems

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  16. Titan97

    Newton's law problem on homogeneous flexible rope

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  17. F

    Projectiles and Newtons law help?

    The first question is about Newton's Third Law: A boat is moving north at a velocity v=15 km/h a man on the boat throws a ball horizontally with a velocity u=15 km/h how is the motion of the ball w.r.t the man? For this, I thought that because the boat is moving with the same speed as the...
  18. R

    Finding coeffiecient of friction

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  19. AdityaDev

    Frame of reference and Pseudo forces

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  20. U

    Help to understand Newtons Law

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  21. N

    Free body diagram and applying Newtons law

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  22. BrainMan

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  23. C

    Newtons law and canoe question

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  24. R

    Newtons Law Of Motion Problem

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  25. J

    Using Newtons law and mechanical energy?

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  26. N

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  27. W

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  28. N

    Newtons law Dynamics Question 4

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  29. S

    Differential Equation Involving Newtons Law of Motion

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  30. A

    Three blocks Newtons law help have I got my answers and sign correct ?

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  31. M

    Projectile Motion Calculations for a Shell Fired at 30 Degrees

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  32. S

    Plateau equation from Newtons law

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  33. S

    Using Newtons Law: Friction

    Homework Statement The static friction between the two blocks is .47 and kinetic friction between the block with mass 9.4 kg and the horizontal surface is 0.21.The acceleration of gravity is 9.8 m/s^2 What is the minimum force F which must be exerted on the 9.4 kg block in order that the 0.8...
  34. K

    Newtons law of cooling vs conduction equation in solids

    I know that Newtons law of cooling is useful when a solid is transferring heat to a fluid. And conduction equation is used in solids. My question is: 1) Can Newtons law of cooling be applied in case of solids (apart from Heat conduction equation)? 2) Can Newtons law of cooling be applied in...
  35. A

    Does Newton's Law of Gravitation Account for Horizontal Surface Area?

    Hello, Is there any research available as to whether Newtons Law F = mg should include horizontal surface area as a factor (ie the surface area of opposing masses). Example a pole weighing exactly the same seems heavier when held at one end horizontally to the ground, compared to holding it...
  36. D

    Need help on this question on Newtons law of cooling

    Homework Statement please i need help as have been trying to solve this question: A body cools from 70°C to 50°C in 6mins when the temp of the surrounding is 30°C. what wil be the tempt of the body after another 12mins if the cooling obeys Newtons law of cooling equation: dq/dt =...
  37. M

    Are Newton's Laws Applicable to Component Forces and Resultant Acceleration?

    Homework Statement I just wanted to know if I was correct, when dealing with a Newton law problem that has components. Ʃfx=0 and ƩfY = zero However when we add the forces together then we can use Ʃf=ma thanks Homework Equations The Attempt at a Solution
  38. W

    Newtons Law - backward motion

    Homework Statement A 245 kg motorcyle & rider can produce an acceleration of 3.50 m/s sq while traveling at 25 m/s. At that speed, the forces resisting motion (friction & air) total 400 N. What force does the motorcycle exert backward to produce it's acceleration? Homework Equations...
  39. N

    Newtons Law of Cooling - Determine rate of cooling

    An engine switched off and left to cool naturally will obey Newtons law of cooling. A particular engine is switched off at 105°C when the ambient temperature is 0°C. Its temperature falls according to the equation T=105e-0.025t °C. Where t=time in minutes. c) use calculus to determine the...
  40. D

    Is Newtons law of cooling related to the zeroth law of thermodynamics?

    Being that both laws explain some kind of heat transfer I was wondering if they are in any way related.
  41. A

    Thermo: Newtons law of cooling for radiation

    Homework Statement A cube of copper of mass 4 kg and initial temperature of 110 oC is set to radiatively cool in an environment of 100 oC. (Note: copper has an emissivity of about 0.05. Also, neglect conduction and convection as cooling agents in this problem.) The surface area of the...
  42. L

    Newtons Law Problem involving kinematic equation

    Homework Statement A duck has a mass of 3.0 kg. As the duck paddles, a force of 0.06 N acts on it in a direction due east. In addition, the current of the water exerts a force of 0.13 N in a direction of 60° south of east. When these forces begin to act, the velocity of the duck is 0.12 m/s...
  43. A

    Calculating Friction Forces in a System of Blocks Connected by Cords

    Homework Statement Homework Statement the blocks shown in the figure are connected by flexible, inextensible cords passing over frictionless pulleys. at A, the coefficient fiction is 0.30 while at B, it is 0.40. compute the magnitude and direction of the friction forces and each block...
  44. W

    How Do You Calculate the Forces in a Tug of War?

    I need to find the magnitude of the force exerted from one boy onto another in a game of tug of war and vice versa. Peter weighs 539 N, John weighs 392 N. During the course of the game Peter accelerates at a rate of 3.0 m/s^2. First the magnitude of force Peter exerts onto John. Then the...
  45. morrobay

    Newtons Law of Cooling applied to hot Neon and Hydrogen gas

    Homework Statement 1 mole of Hydrogen gas at 300 Kevin is contained in a thin walled copper container. In container #2 there is 1 mole of Neon gas also at 300 Kevin. The volume= 22.4 liters and surface area ,A = .476 m^2 The surroundings are at 100 deg Kelvin. The specific heat of H2= 5...
  46. P

    Missing something (Newtons law)

    Hello there! I'm trying to solve this in two ways, and i keep getting different solutions. I need to find the force by which M should be pushed for m1 and m2 stand still (compared tom M). There is no friction between anything. First solution: F_{rp} = m_2 \cdot g \: \: \: F_{rp} = m_1...
  47. A

    Calculating Friction and Acceleration for a Grocery Cart on an Inclined Plane

    Homework Statement a grocery cart is being oused with a force of 450 N at an angel of 30degree to the horizontal. if the mass of the cart and groceries is 42kg. a) calculate the force of friction if the coeffcient of friction is 0.60. b) determine the acclecration of the cart...
  48. S

    Two body applications of Newtons law of cooling.

    Homework Statement What's the formula that better describes the temperature as a function of time for an enclosed body of water with certain initial temperature T_a immersed in another body of water of initial temperature T_b? More clearly, I performed an experiment in which I put a...
  49. N

    Newtons Third Law and Force Imbalance

    Homework Statement 1.A 140 kg man pushes a 90 kg man. They are first motionless, as they push larger man moves smaller one backwards. which statement is correct. a)forces are always equal b) larger wrestles always exerts larger force c)when they are motionlesss forces are equal but as they...
  50. V

    Understanding and Applying Newton's Law of Cooling: A Guide

    Homework Statement Newton's law of cooling says that the rate at which the emperature of any object changes is proportional to the temperature difference between the object and its surroundings. So if the temperature of the object is T, and its surroundings are at a constant temperature...
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