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NEWTON’S LAWS Friction - _______________________________________________________________ List the three types of friction. _____________________________________________ Give an example when friction is good. _____________________________________ _______________________________________________________________________ Give an example when friction is bad. _____________________________________ _______________________________________________________________________ Arrange the following pairs of surfaces in order of most friction to least friction: a. a shoe sole and a waxed basketball court _____ b. a shoe sole and the frozen surface of a lake _____ c. a shoe sole and the sidewalk _____ Gravity - ______________________________________________________________ Mass - ________________________________________________________________ Weight - _______________________________________________________________ NEWTON’S THREE LAWS OF MOTION Newton’s First Law of Motion – An object at rest remains at rest until a force moves it. An object in motion stays in motion until a force stops it. What is another name for this first law? _________________________________ Give examples of this first law of motion. Newton’s Second Law of Motion – F=ma Make a triangle for Newton’s second law. If you kicked a soccer ball and a bowling ball with the same force, which will have the greater acceleration? Why? Describe what would happen if you pushed an empty shopping cart and a full shopping cart with the same amount of force. Solve: Zookeepers lift a stretcher that holds a sedated lion. The total mass of the lion and the stretcher is 175 kg, and the lion’s upward acceleration is 0.657 m/s 2. What is the unbalanced force necessary to produce this acceleration of the lion and the stretcher? 1. What is the net force necessary for a 1.6 x 103 kg automobile to accelerate forward at 2.0 m/s2? 2. A baseball accelerates downward at 9.8 m/s 2. If the gravitational force acting on the baseball is 1.4 N, what is the baseball’s mass? 3. A sailboat and its crew have a combined mass of 655 kg. If the sailboat experiences an unbalanced force of 895 N pushing it forward, what is the sailboat’s acceleration? 4. What is the acceleration of a boy on a skateboard if the unbalanced forward force on the boy is 15 N? The total mass of the boy and the skateboard is 58 kg. 5. A brick is resting on a table. The mass is 2 kg. If the table is smooth and frictionless and we pull on the attached string with a force of 12 N, what is the acceleration of the brick? 6. If you are pulling with a force of 20 N on a brick, what is the mass of the birck if you find that it accelerates at 4 m/s2? 7. A rocket ship is on the launch pad. What force will it take to give the rocket an initial acceleration of 50 m/s2 if its mass is 50,000 kg? 8. A flying bird decides to swoop down on some prey. Its mass is 5 kg and it dives with an initial downward acceleration of 15 m/s2. How much force must it exert with its wings to attain this acceleration? Newton’s Third Law of Motion – For every action there is an equal and opposite reaction. Give examples. What Law of Motion is being described? 11. If you are sitting in the back of a pickup truck, you move backward when the truck accelerates. _________ 12. A straw can pierce a potato if the force and acceleration are great. _________ 13. A balloon moves forward when the air is released. _________ 14. An egg will fall into a container when the support beneath it is removed. _________ 15. A kid bounces down on a trampoline. _________ 16. You shove a full shopping cart with a small force and it barely moves. _________ 17. You slam on the brakes when going 75 mph and anyone without a seat belt on goes toward the windshield. _________ 18. You step out of a canoe and the canoe goes backward. _________