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Transcript
Name: ______________________________ Period: _____ Date: _________________________ Self Assessment: Newton’s Laws of Motion 1. Defined unbalanced forces. How can you tell by looking at an object if the forces on it are unbalanced? 2. Explain what inertia is and what other property of matter it depends on. 3. Which object has more inertia, a golf ball or bowling ball? Explain. 4. Earth is pulling me down. We call that gravity. If gravity is the action, what is the equal and opposite reaction? Identify which Law of Motion each is by placing a 1, 2 or 3 in the blank 5. _______ You’re in a car that slams on the brakes and you go flying forward 6. _______ When you hit a nail with a hammer, they both feel the same force 7. _______ The nail in #2 moves more than the hammer does. 8. _______ I can throw a baseball farther than a shotput. 9. _______ When I throw the baseball, it would go straight, if it weren’t for gravity and air resistance. 10. _______ It takes more effort to push a full shopping cart than an empty one. 11. _______ The weight of an object is its mass times the acceleration due to gravity. 12. _______ I hit a ball with a bat. The same force is exerted on both objects. 13. _______ I spin a yoyo in a circle. If I let go of the string, it flies off in a straight line. True or False. Explain. 14. When forces are balanced something does not move. 15. When forces are balanced something moves at a constant speed. 16. When forces are balanced something accelerates. 17. When forces are unbalanced something does not move. 18. When forces are unbalanced something moves at a constant speed. 19. When forces are unbalanced something accelerates. 20. Draw the forces acting on a ball as I drop it. 21. Draw the forces acting on a soccer ball while I’m kicking it. 22. Draw the forces acting on a soccer ball after I kick it and it’s flying into the goal. Use the formula F=ma to solve the following. Show your work! Don’t forget the correct units and sig figs. 23. ____________________ What is the acceleration of a truck with a mass of 1200 kg moving because of a 7800 N force? 24. ____________________ What is the mass of a soccer ball that is accelerating at 11.5 m/s/s because of an applied force of 167 N? Answer key__ Name: __ Period: _____ Date: _________________________ Self Assessment: Newton’s Laws of Motion 1. Defined unbalanced forces. How can you tell by looking at an object if the forces on it are unbalanced? Total forces are not equal The object accelerates (changes speed, direction or both) 2. Explain what inertia is and what other property of matter it depends on. Tendency of an object to resist changes in motion Depends on mass. More mass = more inertia 3. Which object has more inertia, a golf ball or bowling ball? Explain. Bowling ball. It has more mass. 4. Earth is pulling me down. We call that gravity. If gravity is the action, what is the equal and opposite reaction? You are pulling back on the Earth! (Why doesn’t the Earth move then? Well, technically it does, but not a whole lot because it has more inertia) Identify which Law of Motion each is by placing a 1, 2 or 3 in the blank 1___ You’re in a car that slams on the brakes and you go flying forward 5. ___ 3___ When you hit a nail with a hammer, they both feel the same force 6. ___ 2___ The nail in #2 moves more than the hammer does. 7. ___ 2___ I can throw a baseball farther than a shotput. 8. ___ 1__ When I throw the baseball, it would go straight, if it weren’t for gravity and 9. ___ air resistance. 2___ It takes more effort to push a full shopping cart than an empty one. 10. ___ 2___ The weight of an object is its mass times the acceleration due to gravity. 11. ___ 3___ I hit a ball with a bat. The same force is exerted on both objects. 12. ___ 1__ I spin a yoyo in a circle. If I let go of the string, it flies off in a straight line. 13. __ True or False. Explain. 14. When forces are balanced something does not move. True…it can be not moving. But it is also true that it can move with a constant speed. 15. When forces are balanced something moves at a constant speed. True. If the forces are balanced there is no change in motion, so it keeps doing whatever it was doing. 16. When forces are balanced something accelerates. False. It takes unbalanced forces to change motion (accelerate) see Newton’s First Law of Motion. 17. When forces are unbalanced something does not move. False. According to Newton’s First Law of Motion, unbalanced forces lead to acceleration…motion. 18. When forces are unbalanced something moves at a constant speed. False. According to Newton’s First Law of Motion, unbalanced forces lead to acceleration (change in speed or direction or both). 19. When forces are unbalanced something accelerates. True. Newton’s First Law of Motion says so. 20. Draw the forces acting on a ball as I drop it. Friction/air resistance Gravity 21. Draw the forces acting on a soccer ball while I’m kicking it. Normal force Friction/air resistance Kick (applied force) Gravity 22. Draw the forces acting on a soccer ball after I kick it and it’s flying into the goal. Friction/air resistance Gravity Use the formula F=ma to solve the following. Show your work! Don’t forget the correct units and sig figs. 6.5 m/s2_ What is the acceleration of a truck with a mass of 1200 kg 23. _ F = ma moving because of a 7800 N force? 7800 = 1200 (a) a = 7800/1200 a = 6.5 (div. both sides by 1200) (2 sig figs) 14.5 kg _ What is the mass of a soccer ball that is accelerating at 24. _ F = ma 11.5 m/s/s because of an applied force of 167 N? 167 = (m) 11.5 (div. both sides by 11.5) m = 167/11.5 m = 14.521739813 (3 sig figs)