Transcript notes
October 3, 2005 Homework: Review ALL labs and notes nightly. FINAL EXAM IN four PERIODS. You will need a calculator today. Newton’s 3rd Law When one body exerts a force upon a second body, the second body exerts an equal and opposite force upon the first body. Pushing a Car: Action-Shove a car forward Re-action-the car pushes back on you with equal force Rowing a Boat: Action-Push the water back with paddle Re-action-the water pushed forward on the paddle making the boat propel forward Shooting a Gun: Action-exploding gun powder pushes bullet forward Re-action-the bullet pushes the gun backwards Momentum Newton called this “quantity of motion.” Momentum = mass x velocity p = mv If either mass or velocity increases, momentum is increased. Momentum units come directly from the mass and the velocity and are written right next to each other. Example: kg·m/sec g·mm/sec 1. What is the momentum of a bird with a mass of .018 kg flying at 15 m/sec north? p = mv p = .018 kg x 15 m/sec p = .27 kg·m/sec 2. A 50 kg child is walking with a velocity of 100 m/min. What is the momentum of the child? p = mv p = 50 kg x 100 m/min p = 50000 kg·m/min 3. A golf ball travels at 16 m/sec, while a baseball moves at 7 m/sec. The mass of the golf ball is .045 kg and the mass of the baseball is .14 kg. Which has greater momentum? p = mv p = .045 kg x 16 m/sec p = .72 kg·m/sec (golf ball) p = mv p = .14 kg x 7 m/sec p = .98 kg·m/sec (baseball) The baseball has more momentum. 4. The momentum of a boat is 100,000 kg ·m/sec with a velocity of 5 m/sec. What is the mass of the boat? p = mv 100,000 kg·m/sec = m x 5 m/sec 5 m/sec m = 20,000 kg Use the remainder of class to complete labs 25 & 26. These are the last two in this series! HOMEWORK: Review completed labs, work on practice problems assigned on Friday, study all vocabulary, and memorize all formulas. Lab Goals Today 1. 2. 3. You must complete labs 25 and 26. If you have extra time at the end of the period: Look back over labs 17 – 26. (We did not do # 19.) Do you have the objectives? Do you have the variables? Do you have the QUESTIONS COPIED? Have you answered EACH QUESTION fully? Did you EXPLAIN your thinking? Do your answers support the objectives? What grade would I give you for each lab? Study for the test! Write your own questions. Quiz your neighbor on vocabulary and formulas. Do you know the formula for speed/velocity? Acceleration? Momentum?