Newtons laws Definition and 121 Threads

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. bremenfallturm

    Find starting velocity from golfer launching ball

    Hello! Hope I got this right. Completely new around here. The image that goes along with the problem is: What I have tried so far can be found below: I do not know if it is a computational error or a physics error, but I tried using WolframAlpha to solve for ##v_0## to validate and did not...
  2. M

    Box on treadmill connected to a spring

    First i show the sketch of the setup: My first attempt was just to balance out the forces on the box. On the sketch below i have shown the situation where the spring is stretched distance L. In this situation we get the equations: Which when solved leads to All good. I then looked at the...
  3. M

    B Proof of inverse square law for gravitation?

    Newton arrived at "there is a force that drives a planet around the star by examining kepler's laws but how did he arrive to inverse square law by kepler's third law (##T^2=\frac {4\pi r^3}{GM}##)? Thank you.
  4. J

    Applications of Newton's laws - coefficient of friction

    https://www.physicsforums.com/attachments/277763
  5. G

    Can Newton's Laws Be Applied in a Rotating Cabin?

    A cabin is accelerating with acceleration a .To apply Newtons laws inside it ,we need to include an accleration -a. Now if this cabin is rotating about a point in a plane,can we apply Newtons laws in it? How?
  6. K

    Investigate Newtons Laws. Intro Physics

  7. T

    Why Does My Relative Density Calculation Not Yield a Numerical Value?

    So I am a bit stuck on this question as my result using the above equations dose not give an numerical value which I assume from the question is needed. So here my method for solving My first thought was that if on the planet the person can throw a rock 10 time further then that it implies in...
  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. S

    What will stop me from going at the speed of light?

    Using Newton's 2nd law F=ma, If you provide a constant force of 1mil Newtons then an object will accelerate at 100m/s. Using V = U + AT I can say that (speed of light) 299,792,458 = 0 + 100T thus T = 2997924.58 seconds or I can achieve speed of light in 35 days or so. Why is this not...
  10. S

    What is the Role of Software Engineering in Biomedical Informatics Research?

    am Samuel Owino, a software engineer for the Institute of Biomedical Informatics Research in Eldoret Kenya. I look forward to contributing to the growth of the forum. cheers!
  11. NoahCygnus

    Motion analysis of an accelerating wedge and a block

    I don't understand the motion of an accelerating wedge and a block. I'd really appreciate if you make me understand the motion in both an inertial and a non inertial reference frame. Here's a figure I have made, a0 is the acceleration on the wedge with respect to an inertial frame, towards right.
  12. unseeingdog

    B Coefficient of Restitution in x and y

    I am currently studying collisions in high school and my teacher told us that, in order to calculate the direction of each object after a 2-body collision, we could change the values in the relative velocity terms of the equation of the coefficient of restitution to the components in x and y. Is...
  13. B

    Forces on a Skydiver during the initial frefall phase of the jump

    Homework Statement A skydiver is jumping out of an airplane. During the first few seconds of one jump, the parachute is unopened, and the magnitude of the air resistance acting on the skydiver is 251N. The acceleration of the skydiver during this time is 5.96 m/s^2 [down]. Calculate the mass of...
  14. M

    What happens if i lift a weight on bathroom scales

    If i am standing on bathroom scales and i lift a weight, what will it do to the reading on the scales? I assume that lifting the weight will involve a force from my arm on to the weight, and an equal and opposite force will then push back, causing be to weigh more?
  15. 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...
  16. 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...
  17. AveryB

    Help with Newtons laws of motion and force?

    If anyone could tell me how to answer these questions that would be fantastic. Thank you so much! 1. A box that weighs 66.2 N on Jupiter is taken to Pluto. The weight of the box on Pluto will be ____. (acceleration on pluto is 0.42) Would you find the mass first? 2. The hand in the image...
  18. B

    Newtons Laws car deacceleration

    Homework Statement A 1900 kg car moves along a horizontal road at speed v0 = 23.6 m/s. The road is wet, so the static friction coefficient between the tires and the road is only μs = 0.218 and the kinetic friction coefficient is even lower, μk = 0.1526. The acceleration of gravity is 9.8 m/s2...
  19. J

    Newton's Cradle: Fascinating Momentum & Kinetic Energy

    I have always found the Newton's Cradle that my daughter bought for me fascinating. With the steel balls as identical as possible then the analysis of the process is simple. Both the momentum and kinetic energy are conserved (assuming negligible losses) on collision. The only way(?) this can...
  20. L

    Equilibrium in Two Dimensions: What Force Does a Hanging Boy Exert on Each Tree?

    Homework Statement a boy on whom the force of gravity is 400 N hangs on to the middle of a rope stretched between two trees. The rope sags in such a way that it makes an angle of 170 degrees at the boys hands. what force does the rope exert on each tree? Homework Equations F=ma The Attempt at...
  21. K

    Two stacked blocks sliding down an inclined plane

    Homework Statement "You are lowing two boxes, one on top of the other, down a ramp. Both boxes move together at a constant speed. The coefficient of kinetic friction between the ramp and the lower box is 0.430, and the coefficient of static friction between the two boxes is 0.779. The lower box...
  22. V

    Newton's First law and KT of Gases

    One of the assumptions of Kinetic Theory states that: A gas is a substance composed of many particles flying about randomly, colliding with one another and with the walls of the container. My instructor mention that we might be required to Know, state, and apply this theory to one of newtoms...
  23. H

    Help with Newton's second and third laws

    Homework Statement Two blocks are pushed to the right so that they move together with increasing speed. Block B remains at the height shown. Ignore friction between the ground and block A but not between block A and block B. The mass of block A is 10kg and the mass of block B is 2kg. Let...
  24. D

    Two stacked boxes and a pulley with a weight attached

    Homework Statement The system shown is released from rest. Mass one (0.450 kg) rests on mass two (0.820 kg) and the coefficient of static friction between the two masses is 0.560 and the same for the mass and the table. Determine the maximum mass for M3 such that the mass one will not slide on...
  25. P

    Does anyone know any childern's books about Newtons Laws or Catapults?

    Hey everyone, Random question. Does anyone know any good childern's books about Newton's laws or catapults? I was thinking about getting a gift for my cousin who is turning 10 soon. He really likes catapults so I was thinking about getting him an educational book about catapults...
  26. Q

    Newtons laws of universal gravitation

    Homework Statement its 3.8 x 10^8 from Earth's core to the lunar's core calculate the gravitational attraction exerted by Earth on the moon Homework Equations ag = GM/ r^2 G= 6.67 x 10^-11 M of earth= 5.98 x 10^24 ... r= 6.37 x 10^6 M of moon= 7.36 x 10^22 ... r= 1.74 X...
  27. KiNGGeexD

    What is the role of friction in Newton's Laws?

    Hi I am stuck with a question which I have attached a photo of, it is one involving friction! I have done a few of these questions already and find it is when I am defining forces etc it's where I go wrong, not the easy computational part:( I also have attached my attempt at the solution and...
  28. M

    Newtons Laws, Finding tension in the tow cable and foce

    Homework Statement Just started tension problems and having some trouble figuring out how to approach the problem. Thanks for any help in advance. Consider a rocket that is taking off and towing a large container of trash. The rocket’s engines exert a force, F, that causes the rocket and...
  29. J

    How can I better understand Newton's laws with examples and explanations?

    I am having a very hard time understanding these two problems I have attached. I have read the chapter in our text over and over again, but do not see the correlation or how to exactly set the problems up. I recently had surgery on my writing hand and missed a large portion of this class, so I...
  30. N

    Newtons laws, dynamics questions

    Homework Statement 1) A 1000-kg Car is parked on a 10 degree slope. Determine the magnitude of the frictional force acting on the car 2) A 2000-kg car traveling at an initial speed of 10m/s skids to a stop with a constant acceleration. The coefficient of friction between the tired and the...
  31. N

    Questions in Newtons Laws and Thermodynamimcs.

    Hi there can anyone please explain to me these questions I am really confused about them. Q: A 15 kg wagon is pulled to the right a force of 45 Newtons. the wagon accelarates at 2 m/s2. what is the net (unbalanced) force accelerating the wagon? (f of g is 10) the book says the answer is...
  32. P

    Newtons laws clarification question

    Homework Statement two questions below in my classical mechanics course (our first homework assignment) and I'm not sure what the questions are actually asking...do they want the equations? descriptions of the laws? names of the laws? I'm confused because question one and two seem very...
  33. P

    Newtons laws on car fuzzy dice

    Homework Statement You have a fuzzy dice with mass .2kg hanging from the rear view mirror. When you step on the gas the dice makes an angle of 25 degrees. what is car's acceleration? Homework Equations F=ma...? Fr=mac..? The Attempt at a Solution Im really not sure where to start...
  34. F

    Need help Newtons laws two diemnsions (vertical plane)

    Homework Statement A gardener pushes down on the handle of a lawnmover, applying a force of 250N. The handle is inclined at an angle 45* to the horizontal. If the coefficient of the kinetic friction between the wheels of the lawnmower and the ground is 0.40, what is the acceleration of the...
  35. S

    Simple Newtons laws question ?

    "Simple" Newtons laws question ? At time t = 0 a particle of unit mass is projected vertically upward with velocity v_0 against gravity, and the resistance of the air to the particle's motion is κ times its velocity. Show that during its flight the velocity v of the particle at time t is...
  36. S

    Application of Newtons laws (Friction related) check my solutions please

    Application of Newtons laws (Friction related) check my solutions please :) Dont forget to check the diagram, as it will probably help you see the problem correctly, don't worry, no need to download diagram attachment to view it. Homework Statement A child pushes a block of wood with a...
  37. E

    Question on banked curve, Application of Newtons Laws

    Homework Statement A turn in the road with a radius of 30m is banked at an angle of 40 degrees. If \mu=.75, what is the minimum and max speed a 1200 kg car can travel without sliding off the turn. Homework Equations F=ma, Mv^2/R, Fw = mg The Attempt at a Solution Alright, so...
  38. O

    Calculate Coefficient of Friction for 41N Bookcase on Ground

    Homework Statement what is the coefficient of friction between a 41N bookcase and the groud, when the bookcase accelerates at .25m/s2? Homework Equations F=ma Forcefriction=μ*force normal The Attempt at a Solution a=.25 m=41 μ=? I have absolutly no idea what i am doing
  39. T

    Newtons Laws - Coefficient of Friction problem

    Homework Statement The Attempt at a Solution I found the acceleration using kinematics equations. I don't know how to find the coefficient of friction though. I need help answering pard b c and d If you could give me the equations and explain. Just knowing how to do this one...
  40. T

    Need help with Newtons laws. finding normal force.

    Homework Statement It includes a diagram so i just took a screenshot of the question. I don't undertand how to do this problem Thanks
  41. A

    Does a rocket/spacecraft moving in space violate Newtons laws?

    How does a spacecraft move in space where there is vacuum and nothing to provide normal reaction for the motion?
  42. Vorde

    Use of Calculus in Newtons Laws

    Why do I see Newtons 3 laws (mostly 2 and 3) given using differentials (F=dp/dt etc...) when it is far simpler to use the basic form F=ma (and the same for the 3rd law), is there an advantage to the more complicated form?
  43. V

    How Does Newton's Second Law Apply to a Bird Sitting on a Wire?

    Homework Statement fill in the blanks. when a bird of weight W sits on a stretched wire, The tension in the wire is__________ Homework Equations Force(external)=mass*aceeleration The Attempt at a Solution tension should approach to infinity...
  44. A

    Problem with Newtons Laws of Motion

    Homework Statement There are 2 blocks, one of mass m kept over other of mass 2m. Pls. refer to the diagram. The question is : the minimum value of u (coefficient of friction) between the 2 blocks for no slipping is : (a) F/mg (b) F/3mg (c) 2F/3mg (d) 4F/3mg My answer is coming as (b) but...
  45. I

    Conceptual Question [Newtons Laws]

    When you sit in the passenger seat, why do you feel pushed up when you make a left turn? Explain using Newton's laws of motion.My Guess: Newtons third law states there is a reaction for every action. So when you turn left the opposite reaction would be you turning right? IDK LOL :|
  46. S

    New to physics and with Newtons laws

    What force is required to accelerate a 10g bullet from rest to 200m.-1 in a rifle barrel 50cm long i don't need the answer just how to work it out
  47. K

    Solving for a Train Without Knowing Mass

    A train is traveling up a 3.73 degree incline at 3.25 m/s when the last car breaks free and begins to coast without friction. A) How long does it take for the last car to come to rest momentarily? B) How far did the last car travel before coming to rest? Newtons Second Law I know...
  48. P

    How to Find Coefficient of Kinetic Friction?

    Homework Statement A man is pulling a wagon up a 50° up a hill. His nephew of in unknown mass sits in the wagon. After pulling the wagon 30 meters up the incline, the man slips and falls releasing the wagon. The sled, starting from rest, slides down the incline. After traveling 30 meters the...
  49. P

    Newtons laws: Seem's simple but not for me

    Homework Statement given initial coordinates, r(0), r'(0) and F(r,r',t) find r(t) Homework Equations r''(t) = F(r(t), r'(t), t) / m The Attempt at a Solution have no idea where to start. some hint please, seem's pretty simple but not striking me.
  50. A

    How Do You Calculate the Magnitude of the Second Force?

    Homework Statement Two forces act on a 39 kg mass to give it an acceleration of 26 m/s^2 in the positive x direction. If one of the forces acts in the negative y direction with a magnitude of 450 N, what is the magnitude of the second force. Answer in units of N. Homework Equations Fx:ma...
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