What is Newton's law: Definition and 351 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. P

    Second Newton's law in rotation with pulley.

    Homework Statement The rope doesn't slide on the pulley, it's mass is negligible and it doesn't stretch .The pulley's moment of inertia is 0.00300 kg * m^2 with a radius of 10 cm. As the first mass goes down the rope's friction generates a moment of force of 0.150 N*m opposed to the angular...
  2. A

    Newton's law of universal gravitation

    Homework Statement [/B] Two 100-kg thrill seekers are diving into a neutron star. The neutron star’s mass is 1.1 solar masses and its radius is 12.0 km. For safety, they tie themselves together with a cord 10m long, so that as Melvin reaches the surface of the neutron star, Fred is 10.0 m...
  3. alexandria

    What are the roles of friction and footwear in bob-sledding?

    Homework Statement Homework Equations no equations required The Attempt at a Solution ok so i collected some information about bob-sledding, but i don't know if I've identified the role that friction plays for the athlete and their shoes in the sport, and I've only come up with one...
  4. alexandria

    How do I calculate distance using Newton's Second Law for a puck on a stick?

    Homework Statement [/B] Homework Equations d = v1(t) + ½ a (t)^2 Newtons second Law The Attempt at a Solution ok, so i know that once the puck leaves the stick, the only force acting on it would be the frictional force (1.0 N). From reading other forums, i guess i need to calculate the...
  5. G

    For 2) wouldn't there also be an equal and opposite force on block B by block A?

    Three blocks, each of mass 13 kg are on a frictionless table. A hand pushes on the left most box (A) such that the three boxes accelerate in the positive horizontal direction as shown at a rate of a = 1.4 m/s2. 1)What is the magnitude of the force on block A from the hand? 2)What is the net...
  6. J

    A 300 kg rocket sits on a launch pad. What is the thrust nee

    Homework Statement A 300 kg rocket sits on a launch pad. What is the thrust needed to obtain a thrust to weight ratio 3:1? Homework Equations The Attempt at a Solution 300.0 kg x 9.817 m/s2 = 2945.1 N i know this is not the correct answer, but i have no idea where to start. can someone...
  7. B

    Question for sliding object

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  8. C

    Newton's law of viscosity in 3D, used to derive Navier-Stoke

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  9. M

    What is the Tension and Acceleration in Newton's Law of a Sled Problem?

    Homework Statement This is a problem from a post back in 2006. I have a fairly good understanding of how to do it; however, there is one part about the answer that I cannot figure out at all. (See the relevant equations) Problem: A 5kg penguin sits on a 10kg sled. A horizontal force of 45 N is...
  10. alex740rider

    Need help with Newton's Law of Physics

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  11. M

    Newton's Law of Cooling temp graph

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  12. M

    Newton's Law System With Both Frictions

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  13. Einstein's Cat

    How Is m1 Isolated in Newton's Law of Gravitation Equation?

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  14. C

    MHB What is the Solution to Part B in Newton's Law of Cooling Problem?

    Dear Everyone, I need some help figuring part b in this problem. In the book states, "According to Newton's Law of Cooling, if an object at temperature T is immersed in a medium having a constant temperature M, then the rate of change of T is proportional to the difference of temperature...
  15. VaioZ

    FBD for Newton's Law of Motion Problem

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  16. Titan97

    Newton's Law: Relation b/w tA & tB

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  17. Titan97

    Finding Normal Reaction between Wedge and Block

    Homework Statement A block of mass m is kept on a smooth wedge of angle α and mass M which is in turn kept on a smooth floor. When the system is released from rest, calculate the force exerted by block on the wedge. Homework Equations None. The Attempt at a Solution Let the block a have a...
  18. Titan97

    Newton's law problem on homogeneous flexible rope

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  19. K

    Box Pushed Up an Incline Ramp: Basic Newton's Law Questions

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  20. Remixex

    Hooke's and Newton's law to find Second order ODE

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  21. J

    Derive Newton's Law of Cooling

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  22. S

    Covariant form of Newton's law of gravity

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  23. T

    Slight rearrangement of Newton's Law

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  24. R

    Measuring Mass without Newton's Law: Possible?

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  25. K

    Free body diagrams and Newton's Law

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  26. Calpalned

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  27. andyrk

    Understanding Newton's Law of Cooling and Its Derivation | dQ/dt = KA(dT/dx)"

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  28. R

    Need help with Newton's Law of Cooling math problem

    A detective finds a murder victim at 9 AM. The temperature of the body is measured at 90.3-degrees Fahrenheit. One hour later the temperature of the body is 89.0-degrees Fahrenheit. The temperature of the room has been maintained at a constant temperature of 68-degrees Fahrenheit. Estimate the...
  29. L

    Galilean Relativity and Newton's Laws

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  30. B

    Coulomb's law vs. Newton's law of gravitation?

    What would be the easiest way to describe the similarities and differences between the two laws, other than the fact that their formulas are built similarly and they use different measurements. Any input would be great; I am currently having a brain block! Coulombs Law:F=K (q1*q2)/r^2 Newtons...
  31. A

    Understanding Newton's Law of Cooling: Definition, Equation, and Application

    If the temperature of an object with temperature T(t) is place in a room with the ambient temperature Ta, Newtons Law of Cooling is defined as dT / dt = k (T(t) - Ta), correct? This implies we would need a negative k-value. Wouldn't the equation therefore be described better if T(t) and Ta...
  32. L

    Tension in a string between two blocks

    Homework Statement Two masses M1 = 6.90 kg and M2 = 3.10 kg are on a frictionless surface, attached by a thin string. A force of 48.1 N pulls on M2 at an angle of 31.3° from the horizontal as shown in the figure. Calculate the tension T in the string. Homework Equations T=ma a=g(m2/(m1+m2))...
  33. B

    Newton's Law of Universal Gravitation equation(s) ?

    Homework Statement I am currently reading about Newton's Law of Universal Gravitation and I am so confused as to why there is a negative sign in front of the equation Fg = (G* m1m2)/r^2. Homework Equations Fg = (G* m1m2)/r^2 There is a vector form of the magnitude of the gravitational force...
  34. F

    Newton's law of cooling for a cylinder

    Homework Statement Suppose we have a cylinder of radius R, in an environment with temperature Tenv, and heat is generated in the wire at a rate P per unit volume (for example due to a current - the exact nature is irrelevant). The heat flux from the surface of the wire is A(T(R)-Tenv) for...
  35. G

    Initial Gyroscopic Precession Using Forces

    I think I more or less understand how a gyroscope precesses--at least mathematically and in terms of torque/angular momentum. My question here is: how does the gyroscope start precessing in the first place? The external forces on the center of mass are entirely vertical. Given that Newton's...
  36. N

    Free body diagram and applying Newtons law

    hello! this is a question that iv been working on and can't seem to figure it out, i checked out the other two threads on this same question but they were of no help, anyway here it is: A wedge with mass M rests on a frictionless horizontal table top. A block with mass m is placed on the wedge...
  37. O

    Can Numerical Simulations Accurately Predict Orbital Precession?

    If we had a literal two body system (point masses M and m), with one orbiting the other according to Newton's Law of gravitation, would there be orbital precession? Or would they map out the same ellipse each time?
  38. G

    Measuring Light Frequency: Does Newton's Law Apply?

    Can anyone tell me if the following is correct? Traveling directly towards a source of light at some constant speed, we will measure its frequency to be higher (compared to rest frequency) than what we would expect when using Newton’s laws. Just as traveling away from the source, we would...
  39. M

    How Do You Calculate Impulse and Force in a Racquetball Collision?

    Question A 0.0420-kg hollow racquetball with an initial speed of 12.0 m/s collides with a backboard. It rebounds with a speed of 6.0 m/s. a. Calculate the total impulse on the ball. b. If the contact time lasts for 0.040 s, calculate the average force on the ball. What I did on the test...
  40. L

    Newton's second law, how to write it?

    Very stupid question, but I am writing out my problem and need this formula; in typed symbols, so I can copy and paste it into my document. Like √ Hope that makes sense... Thanks!
  41. AdityaDev

    Conserving Angular Momentum (Rigid Body Dynamics)

    Lets say i have a rod (length = L) hinged at one end (A).It is initially at rest.Now if an impulse (J) acts on the other end (B),can i conserve the angular momentum about A(the hinge)? that is can i write: JL=Iw?(I=moment of inertia,w=angular velocity) this is what i saw in the book. My Doubt...
  42. P

    How do I find the acceleration in Newton's 3 Laws Problem?

    Homework Statement The 20.0 kg box is being pushed with a 45.0N Force acting at an angle of 25.0*. The coefficient of kinetic friction on this surface is 0.150. Find the acceleration Homework Equations F=ma Fy=0 Fx=0 The Attempt at a Solution So I attempted this so far (sum)Fy=0 Py+Fn-Fg=0...
  43. HTT

    Newton's law of motion -- crates & strings & friction

    Homework Statement three boxes connected by strings. given the mass of each box, coefficient of static and kinetic friction, and a constant speed of 2.0 m/s I want to know how to get force by a given speed...! Also, at a constant speed, how do I get to know the acceleration? does a = 0? if a =...
  44. D

    Thermal Conduction and Newton's Law of Cooling

    Fourier's law of thermal conduction states that \mathbf{j}=-k\nabla T, where \mathbf{j} is the heat flux. Integrating both sides of this equation over a closed surface gives the equation \frac{dQ}{dt}=-k\int \nabla T \cdot d\mathbf A. If there is a temperature discontinuity across this...
  45. I

    Newton's LAW vs Einstein's THEORY

    Hello I was just thinking about the Newton's law of gravitation and Einstein's theory of relativity. Newton's law of gravitation was inferred by Newton , probably based on some earlier experiments and Einstein's theory of relativity takes its inspiration from Michelson Morley experiment. Both...
  46. genxium

    How is Eikonal Equation analogous to Newton's Law?

    I read this from a lecture note(attached) of Geometric Optics. It's said that the eikonal equation for light rays \frac{d}{ds}(n(\vec{r})\frac{d\vec{r}}{ds})=\frac{\partial n}{\partial \vec{r}} is analogous to Newton's Law, however it doesn't tell which Newton's Law is referred to. (In the...
  47. I

    MHB How Does Newton's Law of Cooling Apply to a Roast Turkey's Temperature?

    Newton's Law of Cooling states that the rate of cooling of an object is proportional to the temperature difference between the objects and its surroundings. Suppose that a roast turkey is taken from an oven when its temperature has reached $200^oF$ and is placed on a table in a room where the...
  48. N

    Newton's law question (pulley)

    Homework Statement Block A has a weight of 400N and block B has a weight of 100N. The coefficient of friction between all surfaces of contact are μs = 0.7 and μk = 0.2. Knowing that θ = 60°, determine the acceleration of block A and the tension in the cord. Assume block A is moving downwards...
  49. S

    Newton's Law conceptual question

    Homework Statement Two boxes of masses m and 3m are stacked. The surface between the more massive box and the horizontal surface is smooth and the surface between the boxes is rough. If the less massive box does not slide on the more massive box, what is t he static friction force on the...
  50. M

    Newton's Law and Friction (Ramp problem)

    Homework Statement A block is placed on a incline plane. A 21 N force is required to push the block up the incline with constant velocity. What is the weight of the block? Answer in units of NHomework Equations The force pushing the block=21 N with an angle of 13 degrees. The ramp has an...
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