* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download 06 Newton`s Laws of Motion
Survey
Document related concepts
Brownian motion wikipedia , lookup
Center of mass wikipedia , lookup
Hunting oscillation wikipedia , lookup
Relativistic mechanics wikipedia , lookup
Mass versus weight wikipedia , lookup
Seismometer wikipedia , lookup
Work (physics) wikipedia , lookup
Classical mechanics wikipedia , lookup
N-body problem wikipedia , lookup
Rigid body dynamics wikipedia , lookup
Centripetal force wikipedia , lookup
Newton's theorem of revolving orbits wikipedia , lookup
Modified Newtonian dynamics wikipedia , lookup
Classical central-force problem wikipedia , lookup
Transcript
Forces change the motion of an object in very specific ways. So specific in fact that scientist and inventor, Sir Isaac Newton (1642-1727) was able to find commonality in all things in the universe. He was very original in naming them the 1st, 2nd and 3rd Laws of Motion. These laws describe the effects that forces have on objects. 1 Newton’s 1st Law of Motion – Inertia INERTIA the tendency for an object to resist its change in motion. Basically, it wants to keep doing what it’s doing. No mom, I don’t want to go! 1st Law states that… An object in motion tends to stay in motion, and an object at rest tends to stay at rest until another force acts upon that object. 2 Newton’s 1st Law of Motion - Continued Think about it like this…the book is sitting on the table (it is at rest). The book will stay there until (remain at rest) until another force moves it (the outside force). 3 Newton’s 1st Law of Motion - Continued Another way to think about it is that the greater the mass of the object – the greater it’s inertia – the greater its’ resistance to move. Which wrestler would have the greatest inertia? Why? Let’s look at a few examples of the 1st Law of Motion in action! http://www.youtube.com/watch?v=WPngMOfJcFw http://www.youtube.com/watch?v=uOSBC0SXVR4 http://www.youtube.com/watch?v=iDGvBWmUcFU Newton’s 2nd Law of Motion - Acceleration When the golfer hits the ball, where is the ball going to go? Wherever they hit the ball, hopefully in the direction of the pin! 2nd Law states that… a force acting on an object causes the object to accelerate in the direction of that force. 5 Newton’s 2nd Law of Motion - Continued Let’s think about this one… if the Jorge kicks the soccer ball – which direction will the soccer ball go? Force causes acceleration of the object to accelerate in the direction of that force (the kicking of the ball). 6 Newton’s 2nd Law of Motion - Continued Another way to look at the 2nd law is that force causes acceleration. The greater the mass – the greater the resistance to acceleration. Think about it like this… If the blue truck has a mass of 25,000kg and the red truck has a mass of 30,000kg which truck is going to take longer to speed up? Right, the RED Truck because it has a greater mass…5000kg more than the BLUE truck! 7 Newton’s 2nd Law of Motion - Continued Let’s look at a video of the 2nd Law of Motion in action! http://www.youtube.com/watch?v=UhCG0qoY9Dc 8 Newton’s 2nd Law of Motion – The Formula Force = Mass X Acceleration divide F m F = ma a multiply Acceleration units = m/s2 Mass units = kilograms (kg) Force units = kg.m/s2 OR Newton 9 Newton’s 2nd Law of Motion – Calculations Problem: What force is exerted on a 1000kg car accelerating at a speed of 15m/s2? GUESS Read the problem, draw a picture and write down what is given in the problem. 1000kg GUESS Given M = 1000kg A = 15m/s2 15m/s2 Write down the unknown variables in the problem. Unknown Equations Needed Substitute including units Solution Force 10 Newton’s 2nd Law of Motion – Calculations Problem: What force is exerted on a 1000kg car accelerating at a speed of 15m/s2? GUESS Given M = 1000kg A= 15m/s2 Write down the equation needed to solve the problem. Unknown Force Equations Needed F = ma Substitute including units F = 1000kg x 15m/s2 Solution F = 15,000 kg.m/s2 OR F = 15,000 N GUESS Substitute the known variables into the equation including the UNITS. GUESS Solve the equation including the UNITS. 11 Do problems 1-3 in your notes. Using all the correct steps! 12 Newton’s 2nd Law of Motion – Gravity The acceleration for any object moving under the sole influence of gravity on Earth is 9.8m/s2. Any moving object being acted upon ONLY by the force of gravity is said to be "in a state of free fall” because these objects do not encounter air resistance. 9.8m/s2 13 Newton’s 2nd Law of Motion – Gravity Diagram Assuming that the position of a free-falling ball dropped from a position of rest is shown every 1 second, the velocity of the ball shown to increases as the time increases. What relationship do you notice about the distance per every 1 second? So…what type of acceleration does the ball have? Positive or Negative. 14 Newton’s 2nd Law of Motion – Gravity More on this later when we discuss potential and kinetic energy…. But for now, all you need to remember is that acceleration for any object moving under the sole influence of gravity on Earth is 9.8m/s2. 15 Newton’s 3rd Law of Motion – Action/Reaction 3rd Law states that… for every ACTION, there is an equal and opposite REACTION. Action / Reaction forces act in PAIRS. 16 Newton’s 3rd Law of Motion – Continued In this example, when the lady is walking, her feet push against the ground while the ground pushes against her feet. Thus action/reaction – pair is the feet and ground pushing off of one another. 17 Newton’s 3rd Law of Motion - Continued Another example: Let’s think about this one…what are the pairs of forces that are acting against each other in order for the shuttle to launch? Let’s look at how the 3rd Law of Motion made the NASA affected the astronauts. http://www.youtube.com/watch?v=PrJnWTcW55s 18 Newton’s 2nd Law of Motion – Momentum The property of a moving object due to both its mass and its velocity. MOMENTUM An increase in either mass or velocity causes an increase in momentum. For example, if both football players had the same mass of 95kg, but the one in the Yellow helmet was traveling at 10m/s and the one in the Orange helmet was traveling at 12m/s, would that make a difference? Let’s find out… 19 Newton’s 2nd Law of Motion – Momentum Formula Momentum = Mass X Velocity divide P m P = mv v multiply Velocity or Speed units = m/s Mass units = kilograms (kg) Momentum units = kg/m/s 20 Newton’s 2nd Law – Momentum Calculations Problem: What is the momentum of the football players in the orange and yellow helmets? Which player has the greater momentum? G U E S S in order to solve the problem! Remember both players had the same mass of 95kg, but the one in the Yellow helmet was traveling at 10m/s and the one in the Orange helmet was traveling at 12m/s. 21 Newton’s 2nd Law – Momentum Calculations GUESS Given Read the problem, draw a picture and write down what is given in the problem. V = 10m/s V = 12m/s M = 95kg M = 95kg Unknown V = 12m/s M = 95kg Momentum V = 10m/s Momentum M = 95kg GUESS Equations Needed Substitute including units Solution Write down the unknown variables in the problem. 22 Newton’s 2nd Law – Momentum Calculations Given V = 12m/s M = 95kg V = 10m/s M = 95kg Unknown Momentum Momentum Equations Needed Substitute including units Solution P = mv P = 95kg x 12m/s P = 1140 kg.m/s P = mv P = 95kg x 10m/s P = 950 kg.m/s GUESS Write down the equation needed to solve the problem. GUESS Substitute the known variables into the equation including the UNITS. GUESS Solve the equation including the UNITS. 23 Newton’s 2nd Law – Momentum Calculations Back to our original questions… Problem: What is the momentum of the football players in the orange and yellow helmets? P = 1140 kg.m/s P = 950 kg.m/s Which player has the greater momentum? Orange Even though they had the same mass, did it make a difference that the orange player was traveling at a greater velocity in terms of momentum? Absolutely! 24 Do problems 4 & 5 in your notes. Using all the correct steps! 25 In the examples given in your notes, identify if they are representing Newton’s 1st, 2nd or 3rd Laws or multiple laws. 26