What is Newton's laws: Definition and 478 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
  1. K

    How Do You Apply Newton's Laws to Calculate Forces on a Lawn Mower?

    A person pushes a 13.0 kg lawn mower at constant speed with a force of 84.0 N directed along the handle, which is at an angle of = 49.0° to the horizontal. (a) Calculate the horizontal retarding force on the mower (b) Calculate the normal force exerted vertically upward on the mower by...
  2. M

    How Does Air Pressure Relate to Newton's Laws?

    I would like to review some principles, as well as pose some questions, to this highly intelligent community. As such, feedback of ideas, or comments, or even snotty remarks would be appreciated. Classical physics is built on Newton's laws. As such, Newton's laws always apply somewhere...
  3. R

    How Does Acceleration Occur Despite Equal and Opposite Forces?

    I am doing a bit of review and have discovered something I haven't thought about before. We all know Newton's third law (Fab)=-(Fba). So, how can there be acceleration? Say that Fab is 10N, then -Fba is -10N...10N - 10N = 0N. In an action reaction pair, if this net force is 0N...how can there be...
  4. S

    What Is the Optimal Distance D for Minimum Time on a Frictionless Track?

    Hello all, I never really had a great deal of trouble with physics until just recently and this place looks like a great place to learn. I am having problems with the following question: A frictionless track is to be built as shown, with L=3.20 m and H=2.90 m. In order to get the cart to...
  5. I

    How Do Newton's Laws Explain the Motion of a Boat When Stepping Off?

    Newton's Laws-- 2 Questions-- Help Please Hey everyone I have two questions and any help on them would be greatly appreciated. Thanks a lot in advance. Problem #1 A person steps onto a dock off a boat that is tied securely and close to the dock. In another case, a person steps off a boat...
  6. J

    Some guidance please Newton's Laws

    A1000N crate is being pushed across a level floor at a constant speed by a force of 300N at an angle of 20 degrees below the horizontal. (a) what is the coefficient of kinetic friction between the crate and the floor I was able to find this which is = .26 (b) If the 300N force is instead...
  7. N

    Physic homework (kinematics, Newton's Laws and Relative motion/velocity)

    I have this homework problem that I really need help on. Thank you for your time Train A is traveling down a long straight track at a speed of 30m/s. The train A is 0.40km long and the last car at the very end of the train has a cannon mounted on it. Neglect the height of the cannon with...
  8. T

    Description using Newton's laws

    Let's use the scenerio of a car going from uniform motion, to a turn to the left. I'm trying to describe this in relation to Newton's laws in hopes to get a greater understanding. What I know is that objects in the car are affected by Newton's first law, which states (among other things) that...
  9. P

    How Do Newton's Laws Apply in Calculating Contact Force Between Boxes?

    Hi. I have a physics question. I cannot get the right naswer. The question: Three boxes rest side-by-side on a smooth horizontal floor. Their masses are 1.10 kg, 3.45 kg, and 5.55 kg, with the 3.45 kg one in the center. A horizontal force of 20.0 N pushes on the 1.10 kg mass which...
  10. S

    Applying Newton's Laws to Exercise: Understanding the Physics of Fitness

    I was wondering if anybody can help me out on this one.. I am doing a small project that requires me to: Write how Newtons laws relate to exercise, and give an example for each law.
  11. S

    Demonstration and Newton's Laws

    A stone hangs by a fine thread from the ceiling and a section of the same thread dangles from the bottom of the stone. If a person gives a sharp pull on the dangling thread, the bottom string will break, but if he slowly pulls the bottom string the top string will break. After seeing this...
  12. S

    Newton's Laws: Understanding Force & Mass

    Hi everyone! I need some help. 1.)A .2 kg rock is thrown upward with an initial speed 15 m/s. What is the force on the ball in N when it reaches its maximum height? Would I use kinematics to find the max height then use F=ma? If so how? The answer is 2 2.) A woman whose mass as the...
  13. S

    Solving Newton's Laws to Find Total Force - Physics Test Prep

    An athlete whose mass is 93.0 is performing weight-lifting exercises. Starting from the rest position, he lifts, with constant acceleration, a barbell that weighs 500 . He lifts the barbell a distance of 0.700 in a time of 2.10 . Use Newton's laws to find the total force that his feet exert...
  14. I

    Help: Newton's Laws - cement bag at rest.

    Q: A bag of cement of weight 339 N hangs from three wires as suggested in the figure below. Two of the wires make angles and with the horizontal. If the system is in equilibrium, find the tensions in the wires? The answer requires T1, T2, T3. I know T3 = Fgravity = 339N. I made a...
  15. J

    How Does Newton's Third Law Apply to a Rebounding Nitrogen Molecule?

    Here is the question I'm having trouble with: The average speed of a nitrogen molecule is about 6.70x10^2 m/s, and its mass is about 4.68x10^ -26 kg. (a) If it takes 4.20x10^ -13 s for a nitrogen molecule to hit a wall and rebound with the same speed but moving in an opposite direction...
  16. S

    What is the Acceleration and Direction of an Elevator Based on Scale Reading?

    A person stands on a bathroom (?) scale in a motionless elevator. When the elevator begins to move, the scale briefly reads only 0.75 of the person's regular weight. Calculate the elevator's acceleration, and find the direction of acceleration. The only thing that I really got is that the...
  17. C

    Newton's Laws and Net Force: Checking My Understanding

    please help me check my answers, cause if i get one answer wrong, it's a big point deduction. i don't really like doing my homework online. here it goes... 1.) An object cannot remain at rest unless which of the following holds? A.)The net force acting on it is zero. B.) The net...
  18. K

    General relativity and Newton's laws

    Is the gravitational force acting on a particle of mass m, on the surface of a sphere of radius 10^24 metres and with a mass of 10^52 kg given by G x10^52 m / (10^24 ) ^ 1/2 - the Newtonian value - or is the mass density high enough for general relativity to be required to get a sensible...
  19. A

    Can Scientists Prove Newton's Laws?

    Hello fellow scientists! I wanted to know if anyone could prove Newtons laws to for me. I remember a friend did once but i wasnt paying attention at the time. What i remember was him telling me that F=ma could be broken down into a more complex equation with partial darivatives to solve more...
  20. T

    Can QM be derived from Newton's Laws of motion

    Here is an answer I have just given to a question about the journey of light, which applying its logic you can derive QM and GR. Newton's first law of motion state "Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it."...
  21. B

    What is the acceleration of the block?

    A horizontal force of 100N pushes a 12kg block up a frictionless incline that makes an angle of 25 degree with the horizontal. a) what is the normal force that the incline exerts on the block? b) what is the acceleration of the block? ----------------------------------------------------...
  22. S

    How Do Newton's Laws Apply to a Frictionless Pulley System?

    The problem was pretty simple i thought, but according to the book i get the wrong answer. I think i might be approching the problem wrong. "In the drawing, the weight of the block on the table(block1) is 422N and that of the hanging block(block2) is 185N. Ignoring all frictional effects and...
  23. S

    Exploring Newton's Laws: Andrew's Rope Climbing Challenge

    Newton's laws? there is an athlete climbing a rope in gym class. he gets to a point halfway up the rope and is stationary. someone puts a bag of sand that is equal in weight to the athlete. they are both static and then the athlete starts to climb the rope, slowing and speeding up at random...
  24. A

    Newton's Laws Questions: Understanding Deceleration and Resistance

    Right well there is this question which I am stuck on and could do with some help with! Thanks! A runner decelerates as he runs into a windy exposed area, from a speed of 4 m/s to 2 m/s in 8 seconds. His mass is 60 kg. Assuming he also experiences a frictional force of 3 N, find the size of...
  25. Alethia

    Newton's Laws sailboat problem

    Okay, in my class we've been learning basic problems solved by applying Newton's laws. I understand the general idea, but I get confused with problems like the first one. How would I solve it taking both forces on it into account? On the second problem, I don't know how to solve it because it...
  26. M

    Which one of Newton's laws is this equation from and why?

    Which one of Newton's laws is this equation from and why? a=[(m1-m2)g]/[m1+m2]
  27. M

    Force and Newton's laws (airbag)

    Hi, we're starting our chapter on Newton's Laws and force and I wanted to know if I am approaching the following problem correctly: A car travels 53 km/h and hits a bridge abutment (what's that?). The person in the car moves forward 65 cm (w/respect to the road) while being brought to rest by...
  28. N

    Newton's Laws homework questions

    If anyone could help me with these problems, I'd be eternally grateful ... 1) The distance between two telephone poles is 51.0 m. When a 0.800 kg bird lands on the telephone wire midway between the poles, the wire sags 0.210 m. How much tension does the bird produce in the wire? Ignore the...
Back
Top