Name: ___________________________________ Period: ______ Date: ________________ Ch 10.3 & 11Forces: Pre-Test Match each definition on the left with its correct term on the right. 1. _____ the total amount of momentum before a collision is the same as the total amount afterwards 2. _____ for every action there is an equal and opposite reaction 3. _____ net (total) force = 0, no change in motion 4. _____ force of objects rubbing together when they move; can be rolling or sliding 5. _____ an arrow used to show the magnitude (amount) and direction of a force 6. _____ force that pulls things towards the center of an object, proportional to mass 7. _____ when an object is moving only due to the force of gravity, can only happen in outer space or a vacuum 8. _____ combination of horizontal and vertical motion that makes things move in an arc (parabola) 9. _____ force that opposes motion, air resistance is an example 10. _____ an action on an object that changes its motion 11. _____ mass x acceleration due to gravity, changes when you go to different planets 12. _____ tendency of an object to not want to change A. ag B. balanced force C. elastic collision D. force E. free fall F. friction G. gravity H. inelastic collision I. inertia J. kinetic friction K. Law of Conservation of Momentum L. Law of Universal Gravity M. momentum N. net force O. Newtons P. Newton’s 1st Law of Motion Q. Newton’s 2nd Law of Motion R. Newton’s 3rd Law of Motion S. projectile motion T. resultant U. static friction V. terminal velocity W. unbalanced force X. vector Y. weight motion 13. _____ F=ma; acceleration on an object depends on the net force acting on it and its mass 14. _____ when two objects hit and do not stick together, they bounce off 15. _____ Gm1m2/d2; the force of gravity between two objects depends on their masses and the distance between them 16. _____ when the acceleration due to gravity is balanced by air resistance; you won’t go any faster as you fall 17. _____ the sum of all forces acting on an object 18. _____ force between surfaces that are not moving 19. _____ 10.0 m/s2 20. _____ units that force is measured in; equals 1kg x 1m/s2 21. _____ an object at rest stays at rest and an object in motion stays in motion unless acted upon by an unbalanced force 22. _____ p = mv 23. _____ in a drawing of forces, the sum of all the force acting on an object 24. _____ objects collide and stick together 25. _____ when an object is changing speed or direction or both it is experiencing this 26. How can you tell if the forces on an object are balanced? How will it be moving? 27. How can you tell if the forces on an object are unbalanced? How will it be moving? You drop a golf ball and a bowling ball from the top of your house at the same exact time. 28. Which one will hit the ground first? Why? 29. What forces affect how fast something falls? 30. Which object has more inertia? You shoot a golf ball and bowling ball from a cannon. 31. Which would accelerate faster? Why? 32. What forces affect how fast something accelerates? 33. When you are in a car that turns to the right, why does your body lean to the left? Which of Newton’s Laws of Motion applies here? 34. If you drop a bowling ball from 100 feet high on the Moon and Earth, will it fall faster on the Moon, on Earth, or at the same rate in either place? Why? 35. ________________ A girl has a mass of 40 kg. What is her weight? Explain your answer. 36. ________________ You push a grocery cart with a certain amount of force. The grocery cart has a mass of 20 kg and when you push it, you accelerate it at a rate of 2.0 m/s2. With what force did you push the cart? Show your work below. 37. What forces are acting on the grocery cart in the previous problem? Draw a diagram and label the forces that are acting and use arrows to show the direction that they are acting. Are all of these forces the same strength or are some stronger than others? 38. While being pushed in a rolling chair at a constant speed, you tilt your head up and spit your gum out of your mouth, straight up in the air. If you continue to move at this constant speed, could you catch the gum in your mouth again without changing your position? Or will the gum land ahead of you? Or will the gum land behind you? 39. What forces are acting on the person on the chair in the previous problem? Draw a diagram and label the forces that are acting and use arrows to show the direction that they are acting. Are all of these forces the same strength or are some stronger than others? 40. You punch a wall really, really hard. Is more force applied to the wall or to your fist during the punch? Why is this? 41. What are the action and reaction force pair in the previous problem? 42. Student A pushes a refrigerator with 300 N of force and student B pushes the refrigerator the opposite way with 100 N of force at the same time. Draw and label arrows that are to scale that represent the forces from each student and one that represents the result of the two forces combined. Two identical toy cars collide. Describe each cars final velocity if… 43. they are headed toward one another at the same speed and bounce off each other. (You may want to draw a picture) 44. they are headed toward one another at the same speed and stick together. (You may want to draw a picture) 45. they are headed toward one another at different speeds and they bounce off each other. (You may want to draw a picture) 46. they are headed toward one another at different speeds and they stick together. (You may want to draw a picture) 47. How is the law of Conservation of Momentum shown in the above problems about the toy cars? 48. __________________ A 1000 kg car is going 15 m/s. What is its momentum? 49. __________________ Who has more momentum: a 75 kg swimmer going 4 m/s or a 100 kg fullback going 3 m/s? Explain. Answer key__ Name: __ Period: ______ Date: ________________ Ch 10.3 & 11Forces: Pre-Test Match each definition on the left with its correct term on the right. K__ the total amount of momentum before 1. __ a collision is the same as the total amount afterwards A. ag B. balanced force C. elastic collision opposite reaction D. force E. free fall motion F. friction G. gravity they move; can be rolling or sliding H. inelastic collision I. inertia (amount) and direction of a force J. kinetic friction K. Law of Conservation center of an object, proportional to mass of Momentum L. Law of Universal Gravity M. momentum R__ for every action there is an equal and 2. __ B__ net (total) force = 0, no change in 3. __ J__ force of objects rubbing together when 4. __ X__ an arrow used to show the magnitude 5. __ G__ force that pulls things towards the 6. __ E__ when an object is moving only due to 7. __ the force of gravity, can only happen in outer space or a vacuum N. net force O. Newtons P. Newton’s 1st Law of Motion motion that makes things move in an arc (parabola) Q. Newton’s 2nd Law of Motion R. Newton’s 3rd Law of Motion S. projectile motion is an example T. resultant U. static friction motion V. terminal velocity W. unbalanced force S__ combination of horizontal and vertical 8. __ F__ force that opposes motion, air resistance 9. __ D__ an action on an object that changes its 10. __ Y__ mass x acceleration due to gravity, 11. __ I changes when you go to different planets X. vector Y. weight 12. __ __ tendency of an object to not want to change motion Q__ F=ma; acceleration on an object depends on the net force acting on it and 13. __ its mass C__ when two objects hit and do not stick together, they bounce off 14. __ L__ Gm1m2/d2; the force of gravity between two objects depends on their 15. __ masses and the distance between them V__ when the acceleration due to gravity is balanced by air resistance; you 16. __ won’t go any faster as you fall N__ the sum of all forces acting on an object 17. __ U__ force between surfaces that are not moving 18. __ A__ 10.0 m/s2 19. __ O__ units that force is measured in; equals 1kg x 1m/s2 20. __ P__ an object at rest stays at rest and an object in motion stays in motion 21. __ unless acted upon by an unbalanced force M__ p = mv 22. __ T__ in a drawing of forces, the sum of all the force acting on an object 23. __ H__ objects collide and stick together 24. __ W__ when an object is changing speed or direction or both it is experiencing 25. __ this 26. How can you tell if the forces on an object are balanced? How will it be moving? It will not be accelerating…that is, it will either be at rest or have a constant velocity (both speed and direction) 27. How can you tell if the forces on an object are unbalanced? How will it be moving? It will be accelerating; changing either its speed or direction or both You drop a golf ball and a bowling ball from the top of your house at the same exact time. 28. Which one will hit the ground first? Why? They will hit at the same time (especially if ignoring air resistance) because all objects fall at the same rate…9.8m/s2. The bowling ball has more mass, so gravity pulls more, but also more inertia and their effects “cancel” each other out. 29. What forces affect how fast something falls? Gravity and air resistance 30. Which object has more inertia? Bowling ball because it has more mass You shoot a golf ball and bowling ball from a cannon. 31. Which would accelerate faster? Why? Golf ball. Given the same force, it has a smaller mass so a bigger acceleration 32. What forces affect how fast something accelerates? Net force acting on it…sum of all the forces. If the sum/net force is 0, it still moves, it just won’t accelerate (change speed or direction) 33. When you are in a car that turns to the right, why does your body lean to the left? Which of Newton’s Laws of Motion applies here? Newton’s First Law of Motion You don’t lean to the left…you are an object in motion and you stay in motion at the same speed/direction until acted upon by an unbalanced force…the seat belt, I hope…. 34. If you drop a bowling ball from 100 feet high on the Moon and Earth, will it fall faster on the Moon, on Earth, or at the same rate in either place? Why? Earth…has more mass, therefore more gravity. 400N___ A girl has a mass of 40 kg. 35. ___ What is her weight? Explain your answer. Weight = mass x g (acceleration due to gravity 9.8 m/s2) 400N (I rounded to 10.0 m/s2 and weight is a force, so its measured in N) 40 N_____ You push a grocery cart with a certain amount of force. 36. ____ The grocery cart has a mass of 20 kg and when you push it, you accelerate it at a rate of 2.0 m/s2. With what force did you push the cart? Show your work below. F=ma F = 20 kg x 2.0 m/s2 F = 40 N 37. What forces are acting on the grocery cart in the previous problem? Draw a diagram and label the forces that are acting and use arrows to show the direction that they are acting. Are all of these forces the same strength or are some stronger than others? normal friction applied g Note: applied is greater than friction. Since there’s acceleration forward, the forces are unbalanced. 38. While being pushed in a rolling chair at a constant speed, you tilt your head up and spit your gum out of your mouth, straight up in the air. If you continue to move at this constant speed, could you catch the gum in your mouth again without changing your position? Or will the gum land ahead of you? Or will the gum land behind you? Yes, you can. The gum is moving forward at the same speed you are (object in motion) and the up/down motion has no effect on the forward motion. 39. What forces are acting on the person on the chair in the previous problem? Draw a diagram and label the forces that are acting and use arrows to show the direction that they are acting. Are all of these forces the same strength or are some stronger than others? normal friction applied g Note: friction and applied are the same. Since there’s constant speed, (no acceleration) the forces are balanced. 40. You punch a wall really, really hard. Is more force applied to the wall or to your fist during the punch? Why is this? Same to both. For every action there is an equal and opposite reaction. Your hand moves more because it has less inertia (1st Law) or because with the same force, it has less mass so accelerates more (2nd Law) 41. What are the action and reaction force pair in the previous problem? Action…you hit the wall Reaction…the wall “hits” back. Note: the force pairs happen: At the same time In the same magnitude (amount) In opposite directions On different objects (wall, you) 300 N of force and student B pushes the refrigerator the opposite way with 100 N of force at the same time. Draw 42. Student A pushes a refrigerator with and label arrows that are to scale that represent the forces from each student and one that represents the result of the two forces combined. My scale: 1 block = 25 N. Result is 200N in direction of 300 N Two identical toy cars collide. Describe each cars final velocity if… 43. they are headed toward one another at the same speed and bounce off each other. (You may want to draw a picture) bounce back in opposite directions at same speeds as began. Before: After: 44. they are headed toward one another at the same speed and stick together. (You may want to draw a picture) stick and don’t move Before: After: 45. they are headed toward one another at different speeds and they bounce off each other. (You may want to draw a picture) bounce off, change velocities (directions and speeds) Before: After: 46. they are headed toward one another at different speeds and they stick together. (You may want to draw a picture) stick together move slowly (at ½ difference in speeds) in direction of faster one Before: After: 47. How is the law of Conservation of Momentum shown in the above problems about the toy cars? The system is both cars (not just one). When you add their momenta up before and after and compare, you get the same amount. 20000 kg x m/s ___ A 1000 kg car is going 15 m/s. What is its 48. ___ p = mv momentum? p = 1000 x 15 p = 15000 p = 20000 kg x m (1 sig fig) s same!__ Who has more momentum: a 75 kg swimmer going 4 m/s or a 49. ___ 100 kg fullback going 3 m/s? Explain. They are the same! Swimmer … p = mv p = 75 x 4 p = 300 kg x m s Fullback … p = mv p = 100 x 3 p = 300 kg x m s