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.

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  1. X

    How Would You Apply Newton's Laws With Rock Climbing?

    Applying Newton's Laws With Rock Climbing How Would You Apply Newton's Laws With Rock Climbing? ?
  2. L

    Practical Applications of Newton's Laws: A Science Competition Project

    Homework Statement I have to prove Newton's laws with a practical project, for my school's science competition. This is what I have until now: 3rd law ==> a) Two balls tied with a thread with a spring between them. b) A rocket/balloon... but I don't know how... any...
  3. P

    Newton's Laws of Motion on a car

    Homework Statement Hi, I am taking a correspondance physics course and just wanted to know if I am on the right track with understanding Newton's principles. Roberta drives her 1452 kg car along a straight , level road at a consant velocity of 30.0m/s (E). Her brakes suddenly give out...
  4. S

    Calculating Dynamics: Newton's Laws and Friction on a Stair-Slider

    "John" the stair-slider was recently photographed sliding down a staircase. He has a mass of 98.0 kg when sitting on a carpet lubed up on the bottom with a kg of butter. The staircase is 8.2 meters long and makes an angle of 43 degrees with the horizontal. The butter reduces his frictional force...
  5. P

    Designing an Elevator for a Hospital: Maximum Speed and Newton's Laws Explained

    "You are designing an elevator for a hospital. The force exerted on a passenger by the floor of the elevator is not to exceed 1.6 times the passenger's weight. The elevator accelerates upward with constant acceleration for a distance of 3m and then slows down. What is the maximum speed of...
  6. 8

    Identifying Newton's Laws in Physics-B Situations

    does anybody know where I can find a LOT of situations where I have to identify which law of Newton it fits to? If not, can somebody give me situations in which I have to indentify? This is AP physics-B level so something not that convoluted Thanks
  7. S

    Equilibrium Applications of Newton's Laws of Rotation

    Hi, I am stuck on this problem, any feedback would be greatly appreciated. Thank you... The leaning Tower of Pisa is 55 m high and 7.0 m in diameter. The top of the tower is displaced 4.5 m from the vertical. Treating the tower as a uniform, circular cylinder, (a) what additional...
  8. A

    Simple, but confusing question about Newton's laws

    Ok, if you need to determine a tension in a string that is being pulled by a human that is on a sled (the sled is accelerating outwards). Is the normal force the two weights combined?? I have Friction force + (- Tension)= ma But for the friction force I don't know whether or not I need to...
  9. A

    Finding the Tension in a String Using Newton's Laws

    This problem involves Newton's laws. I got the first half of the problem but I am stuck on the second part. Please take your time to guide me through it, thanks! Problem: A van accelerates down a hill, going from rest to 30 m/s in 6 seconds. During the accceleration, a toy (m=.1kg) hangs by a...
  10. B

    Newton's Laws and Friction Applied to Blocks

    Given: 2 wedge shaped blocks arranged as a rectangle. The bottom block is on a frictionless horizontal surface. Horizontal force Q is applied to the vertical side of the bottom block. Find Q max, the maximum value of Q where there is no slipping, in terms of us, m, and theta. Masses: m and m...
  11. A

    Understanding Forces and Acceleration in Newton's Laws of Motion

    INTRODUCTION: The following is a problem of "Newton's Laws Of Motion". It is a typical problem of this chapter. I am having problems with some parts. THE PROBLEM IN BLACK AND WHITE: "Find the acceleration a_{A}, a_{B} and a_{C} of the three blocks shown in the diagram (not included here)...
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    Newton's Laws Question I don't understand this

    In the apparatus shown, m1 = 2.0 kg, theta = 37°, and the coefficients of static and kinetic friction between m1 and the inclined plane are 0.30 and 0.20, respectively. Figure 4.38, m1 is on an incline, 37 degrees above the horizontal, connected to a pulley which is connected to m2...
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    Help with problems over Newton's Laws

    I need help with these problems that I'm not quite sure on how to do, I have attempted and gotten and answer, but I tend to be wrong... 1. a 0.095 KG pom pom slides along the gym flour with an initial speed of 5.50 m/s. It came to a complete stop in 1.9 m. What is the coefficient of...
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    Newton's Laws: Examples to Explore

    Anyone have any really good examples for Newton's 1st and 2nd Laws?
  15. P

    Understanding Forces in Static and Dynamic Systems

    I am a bit confused, I thought I understood it, but the way the questions are worded seem to suggest I am wrong, which is usually a good indicator... I keep putting things as equal, but it seems a bit of repetitive for everything to be equal. I am using Newton's third law for this. 1...
  16. D

    What forces are missing from the free-body diagram for m1?

    Hi, I have a non-homework question, I hope that is ok. Sometimes, when I solve force problems using Newton's laws, I can easily solve the problem, but I am confused about exactly what law is involved. For example, I was helping someone solve a pulley problem today. This is problem 34 in...
  17. V

    Newton's laws conceptual questions

    1) An elevator with a person in it is being pulled upwards by a cable. Identify all interaction forces in the system. Consider your system to consist othe cable, elevator, the Earth and the person. The Earth pulls down on the elevator with force Mg and the elevator pulls up the Earth with...
  18. V

    How do Newton's Laws work in these situations?

    1) A 5kg box is pulled by a force F horizontally (no angle). There is friction between the box and horizontal surface. Mu_k = .25 and Mu_s = .5. If F=20N find the magnitude of the friction force and the acceleration of the block. I used the formula |f_k| = mu_k * |Normal force| f_k =...
  19. L

    Newton's Laws of Motion Question

    okay, so I've tried this problem and I keep getting it wrong. I would really appreciate some help in solving it. Here is the question: The parachute on a race car of weight 8820 N opens at the end of a quarter-mile run when the car is traveling at 35 m/s. What total retarding force must be...
  20. K

    Numerical Problem based on Newton's laws of Motion

    A 5kg block is resting on the top right hand corner of a 10kg block. The length of the top of the 10kg block is 10m. Find the time taken by the 5kg block on top to slide of the 10kg block completely if the 10kg block is accelerating at 5m/s^2. My work: aB = accleration of the 5kg block aA...
  21. K

    Verifying Newton's Laws: Finding Acceleration & Contact Forces

    Hi I have a problem and a doubt regarding Newton's laws of motion. Consider three blocks of 5,2,5kg respectively placed one over the other and dropped from the top of a tower. (the 5 kg if at the top, 2kg in the middle and the 5kg at the bottom). i) Find the acceleration of each block...
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    Help Improve Newton's Laws of Motion on Wikipedia

    Hi, You have most probably heard about the internet phenomenon Wikipedia, now the world's largest, an encyclopedia that anyone can edit. But currently, the article on Newton's laws of motion is in a poor state. It needs your help to get upto shape. You can edit the page by clicking the edit...
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    Calculating Forces on a Coasting Car: Newton's Laws and Air Drag Calculation

    "a person drives their 1452 kg car along a straight road at a constant velocity of 30 m/s east. their brakes suddenly give out. they put the car in neutral and let is coast for 25 seconds. the air drag decelerates the car to a velocity of 25 m/s east. (assume a frictionless surface)." b)...
  24. C

    Problem with Forces and Newton's Laws

    Hi, I have a problem on my homework for AP Physics. I have the answer from the back but need to figure out why I am not getting the right solution. There is also an angle in the problem and I don't know what I am supposed to use it for or in what equation. The problem is: A 40.0kg wagon is...
  25. G

    Finding Acceleration of Wedge & Mass via Newton's Laws

    Problem: "A smooth wedge of mass M has a triangular cross section with a side inclined at an angle theta to the horizontal base. The wedge can slide without friction along a horizontal support. Placed on the side of the wedge is a mass m that can slide with no friction along the side. Find...
  26. P

    Examples of Newton's Laws of Motion in Practice

    hey, i was wondering if somebody out there may be able to give me examples of Newton's Laws of motion in practise so that I would be able to grasp the concept of the these laws thanks for your time, Pavadrin
  27. T

    Calculating the Force Required for an Exceptional Vertical Jump

    Ok here's my question: An exceptional vertical jump from rest would raise a person 0.80m off the ground. to do this, what constant force would a 70kg person have to exert against the ground? assuming the person lowers himself by 0.2m prior to jumping and remains ina standing position while in...
  28. H

    What Forces are Involved in Newton's Laws of Motion for Two Bodies on a Table?

    Two bodies of masses m1 and m2, are released from the position shown in the figure. If the mass of the smooth-topped table is m3, find the reaction of the floor on the table while the two bodies are in motion. Assume the table does not move. I attempt to find out all the forces acting. There's...
  29. S

    What are the forces acting on an object sliding down a hill?

    homework help! Hi! everyone I am new tp physics and I need help. We had just finished a part on Newtons 1st and 2nd laws and were given a question as follows. An object is sliding down a hill, at an angle 30 degrees to the horizontal. The object has mass 50Kg. If the acceleration of the...
  30. C

    Newton's Laws Of motion Please Reply

    This is my problem: A window washer pulls herself upward using the bucket-pulley apparatus The mass of the person plus the bucket is 70 kg. A) How hard must she pull downward to raise herself slowly at constant speed?...N (b) If she increases this force by 9%, what will her acceleration...
  31. F

    Confirming an observation about Newton's Laws

    When approaching a problem concerning Newton's 2nd law of motion, if I'm dealing with a frictionless inclined plane and know the velocity of an object going up the plane, is it safe to say that the velocity will be the same on the way back down since no friction is present?
  32. S

    Force and tension problems without using Newton's laws

    Hello. I was trying to find a way to solve the tension problems without using Newton’s laws. The problem says: A weight of 200 kg is supported by two wires. Find the magnitude of the tension in each wire. The angle in the top left is 35 and the angle in the top right is 41. I used the law of...
  33. K

    Some Applications of Newton's Laws of Motion

    This is probably really easy, but I can't figure out what to do. A man of mass 80kg (W= 176 lb) jumps down to a patio from a window ledge .50m (1.6ft) from ground. He doesn't bend his knees on landing so his motion is arrested in a distance 2.0cm (.79in) What is the acceleration of the man...
  34. N

    How to Solve a Physics Problem Involving Newton's Laws and Weight Measurements

    Hey, new member here, and I'm stumped on a physics problem. Two weights are tied onto each end of a piece of rope and set on a table. The rope has a scale on it. The two weights are hanging over the edge of the table - one has Fg of 100 N, the other has Fg of 50 N. What does the scale read? My...
  35. R

    What is the net force on the fish in this fishing scenario?

    I'm on the 3rd unit of my physics unit and we're applying Newton's 3 Laws of motion. There's this problem: "A fisherman yanks a fish out of the water with an acceleration of 4.5 m/s^2 using very light fishing line that has a "test" value of 100 N. The fisherman unfortunately loses the...
  36. A

    Questions on projectiles & Newton's laws of motion

    hi there falks i need some hard questions on projectiles & Newton's laws of motion...
  37. M

    Newton's laws violation consequences

    Do not get me wrong when I ask this question. I know laws cannot be violated. However, if Newton's third law were violated, what would the consequences be? Also how would Newton's first and second law be violated and what would the consequences be?
  38. Greg Bernhardt

    Explore Newton's Laws of Motion with Dr. Donald Luttermoser of ETSU

    Author: Dr. Donald Luttermoser of East Tennessee State University
  39. T

    Finding the Acceleration of a Moving Bus Using Newton's Laws

    Hello, Could anyone help me with this problem? "A hammer is hanging by a light rope from the ceiling of a bus. The ceiling of the bus is parallel to the roadway. The bus is traveling in a straight line on a horizontal street. You observe that hammer hangs at rest with respect to the bus when...
  40. L

    Calculating Spacecraft Weight Using Newton's Second Law

    A spacecraft descends vertically near the surface of Planet X. An upward thrust of 25.0 kN from its engines slows it down at a rate of 1.2 m/s^2, but if an upward thrust of only 10.0 kN is applied, it speeds up at a rate of 0.80 m/s^2. Apply Newton's second law to each case, slowing down or...
  41. L

    Can the tanker avoid hitting the reef with its engines back on?

    An oil tanker's engines have broken down, and the wind is blowing the tanker straight toward a reef at a constant speed of 1.5 m/s. When the tanker is 500 m from the reef, the wind dies down just as the engineer gets the engines going again. The rudder is stuck, so the only choice is to try to...
  42. A

    Two questions - Newton's Laws

    A research balloon of total mass M is descending vertically with download acceleration a. How much ballast must be thrown from the car to give the balloon an upward acceleration a, assuming that the upward lift of the air on the balloon does not change? I get m = (2aM)/(g+a), where g is...
  43. S

    Explaining Newton's Laws: Car, Balloons, Weights & Roller Coasters

    my question is about the Newton's laws: 1. if a car suddenly brakes all the objects in the car tends to move forward by a force but a balloon tends to move backward, why? 2. if we tie two strings in two sides of a weight and hang the weight by one string and slowly pull the other string...
  44. E

    Circular Motion of Newton's Laws

    The Earth rotates about its axis with a period of 24.0 h. Imagine that the rotational speed can be increased. If an object at the equator is to have zero apparent weight, (a) what must the new period be? (b) by what factor would the speed of the object be increased when the planet is rotating...
  45. J

    Applying Newton's Laws to general questions.

    Can any explain the following concepts to me? I am clueless. And these are suppose to be general concepts... -Why does a child's wagon seem to fall backaward when you give the wagon a sharp push? -If you walk along a log floating on a lake, why does the log move in the opposite direction...
  46. P

    Motion, Strobe and Newton's Laws

    I have some questions that I need help answering and are due friday september 30th but i need the help to answer them. ok here goes. The question is What is the difference between motion at constant velocity and motion at constant acceleration? Explain your answer. I say that there is no...
  47. O

    How Do You Calculate Mass Using Newton's Laws?

    Newtons Laws? well i tied this prpblem you apply a force of .35 n [up] to a fork and it accelaraion is .15m/s^2 wats its mass in grams well i tried rearanging the force equation m=a/f but i got the worng answer si i thoght i rearanged wrong so i tried swithing the varables but that stil...
  48. P

    Nonequilibrium Applications of Newton's Laws of Motion

    A 292 kg motor cycle is accelerating up along a ramp that is inclined 30.0 degrees above the horizontal. The propulsion force pushing the motorcycle up the ramp is 3150 N, and air resistance produces a force of 250 N that opposes the motion. Find the magnitude of the motorcycle's acceleration.
  49. C

    How Do I Solve These Complex Newton's Laws Problems?

    can someone please help me with these problems? I'm completely lost. 1. Synchronous communications satellites are placed in a circular orbit that is 2.32 x 107 m above the surface of the earth. What is the magnitude of the acceleration due to gravity at this distance? 2. A woman stands on...
  50. R

    Question regarding Newton's laws

    well, my question isn't directly towards Newton's law or anythiing, but its a question on how to solve problems using Newton's law. for example, look at this problem below.. a force of 20N acts horizontally on a mass of 10kg being pushed up a fritionless incline that makes a 30degrees angle...
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