2. What is the Formula that represents the 2 nd Law? 3. Using the above formula, what are the TWO KEY POINTS OF THE LAW? Key Point #1.

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1 Name Date Per # NEWTON S 2 nd and 3 rd Laws of MOTION NOTES and LAB NOTES 1. What does Newton s Second Law State? 2. What is the that represents the 2 nd Law? 3. Using the above formula, what are the TWO KEY POINTS OF THE LAW? Example Problems: A boy pushes a grocery cart forward with a total mass of 40 kg. What is the acceleration of the cart if the net force on the cart is 60N? Key Point #1 Key Point #2 What is the upward acceleration for a helicopter with a mass of 5000 kg if a force of 10,000 N acts on it in an upward direction? 1

2 What is the acceleration of an object moving towards the earth if its mass is 7kg and the force applied to it is 68.6 N? 4. Golf Ball And Ping pong Ball Demo Prediction (Which will hit the ground first?) Observation 5. Explain why they hit the ground at the same time. 6. Calculate the acceleration due to gravity of an apple and watermelon. APPLE WATERMELLON 7. Clarify why some things fall slower in Earth s Atmosphere 2

3 PART 1: Newton s 2 nd Law Keeping the Force Constant but change the MASS DIRECTIONS: Set up a blue car with a 1 oz fishing weight pulling it down. You will pull the car with 100 grams in it (.1 kg) and with 500 grams (.5 kg) and compare the acceleration of your 2 cars. You allow the force of the fishing weight to pull it the distance of the counter. INFORMAL OBSERVATIONS ABOUT THE CARS ACCELERATION Car with.1 kg of mass (light car) Car with.5 kg of mass (heavy car) Time it took: What does that mean about its acceleration compared to the heavier car? Time it took: What does that mean about its acceleration compared to the lighter car? FORMAL CALCULATIONS: Calculate the acceleration of the 2 cars using Newton s. NOTE: Force needs to be measured in NEWTONS and MASS in KG Calculate the Acceleration of the LIGHT CAR : Variables Calculate the Acceleration of the HEAVY CAR : Variables SUMMARY: IF YOU INCREASE THE MASS OF AN OBJECT, WHAT HAPPENS TO ACCELERATION? 3

4 PART 2: Newtons 2 nd Law Keeping the MASS CONSTANT but CHANGING FORCE DIRECTIONS: This time you will ALWAYS KEEP 500 grams (.5 Kg) in your car. However, you will pull the car with 1oz of fishing weight one time and the next time with 4 oz of weight. INFORMAL OBSERVATIONS ABOUT THE CARS ACCELERATION Car with pulled with only 1 oz Car pulled with 4 oz Time it took: What does that mean about its acceleration compared to the car pulled with more force? Time it took: What does that mean about its acceleration compared to the car pulled with less force? FORMAL CALCULATIONS: Calculate the acceleration of the 2 cars using Newton s. NOTE: Force needs to be measured in NEWTONS and MASS in KG Calculate the Acceleration of the car pulled with 1 OZ weight : Variables Calculate the Acceleration of the car pulled with 4 OZ weight : Variables SUMMARY: IF YOU INCREASE THE FORCE PUSHING OR PULLING AN OBJECT, WHAT HAPPENS TO ACCELERATION? 4

5 Name Date Per # 3 rd Laws of MOTION NOTES and LAB Newton s 3rd Law 5

6 LAB SECTION Newton s 3 rd Law Newton s Third Law of Motion = How are action and reaction forces related? Demo 1. Hang the 200g mass from one of the spring scales. What is the reading? 2. Identify the action and reaction forces involved in the spring scale-mass system you have constructed. a. Action = b. Reaction = Have students do this 3. Take the 200g mass off the bottom scale. Connect the two spring scales so that the bottom hooks are connected to each other. Gently pull the spring scales horizontally in opposite directions. Try to get different readings on the scale. Were you able to get different readings on the both scales? Explain why you cannot get different reading on the two scales based on Newtons 3 rd law of motion. Identify Action/Reaction Pairs in the situations below: 4. Push down on your desk: Action 5. Kicking a soccer ball Action 6. Jumping up off the ground Action Reaction Reaction Reaction 6

7 PRACTICE SHEET : Newtons 1 st, 2 nd, and 3 rd Laws 1. Draw a sketch that clearly demonstrates each one of Newton s 3 Laws in the boxes below, then write each one of Newton s 3 laws in the boxes below that. Newton s 1 st Law Newton s 2 nd Law Newton s 3 rd Law Sketch Sketch Sketch Law Law Law 2. Use Newton s second law to explain the following questions a. Why is it easier to kick a soccer ball than a bowling ball? b. When you need to push-start a car, why does it really help to have more than one person pushing? c. In a dog-sled race, a 5 dog team can go much faster than a 2 dog team. Explain why. Write Newton s 3 rd law in your own words: Draw 2 sketches that show Newton s 3 rd law 7

8 Math Problems: Make sure you show your work (except # s 3&4) and include units on each problem 3. When you try to run forward, your feet push the ground backwards. If you push the ground 300 N backwards, how hard does the ground push you? In what direction does it push you? 4. A 500 N weight is sitting at rest on a table. How hard does the table push the weight up? 5. A 100 Kg runner accelerates off the starting line at 5.5 m/s/s. What is the force that the runner presses off the ground with? 6. Mr. Settle s truck has a mass of 1200 Kg. If his engine can apply a force of 5000 N, how fast can it accelerate? 7. If 250 N of force causes a chicken to accelerate at a rate of 5 m/s/s, what is the mass of the chicken? 8. Imagine that a sled is sliding across a flat snowy field, accelerating at 2 m/s/s. What would the acceleration of the sled be if a. The net force on the sled doubled because dude pushed twice as hard b. The dude throws off a bunch of gear and the mass of the sled is halved c. The mass of the sled doubles, but so does the net force d. The mass of the sled doubles, and the force on the sled is divided in half e. The mass of the sled doubles and the force on it quadruples f. The mass of the sled is multiplied by 6 and the force on it triples 8