Review newton's laws

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Review newton's laws

  1. 1. Newton's Law Practice Newton's First Law Newton's First Law states that objects will continue doing whatever they are doing unless a force acts on them. We call this property inertia. Inertia is the tendency of an object to resist a change in motion. For this reason, Newton's first law is frequently called the "Law of Inertia". 1. A small steel ball is placed in the center of a smooth level table. Describe what will happen to the ball if it is not disturbed. Which of Newton's laws of physics does this illustrate? 2. The small steel ball is now given a small momentary push. Describe the motion of the ball until it reaches the edge of the table. 3. An abandoned space ship is drifting deep in interstellar space at a speed of 20,000 m/s. Describe the motion of the space ship if it is not disturbed. 4. A passing salvage vessel decides to investigate the abandoned space ship. A small space-suited figure is seen leaving the salvage ship and moving toward the wreck. Unfortunately the astronaut aims wrong and misses the abandoned ship. What will happen to the astronaut if no further action is taken? Will the astronaut stop moving or continue to move? 5. A skateboard resting on a sidewalk is given a push. It rolls for a distance and then stops. Is this a violation of Newton's first law? Explain. Calculating Force Using Newton's Second Law In each of the following situations, identify which object has the larger applied force and write the name of the object. 1. A bowling ball and an apple are dropped. They accelerate at the same rate. 2. A small car and a large truck leave a stop light side-by-side, and remain next to each other as they speed up. 3. Two cars identical except for color are pulled by spring scales so that they accelerate. The red car accelerates more than the blue car. In each of the following situations, identify which object has the larger mass and write the name of the object. 4. Two different cars, one green and the other yellow, are pulled by spring scales. Both cars accelerate at the same rate. The scale attached to the yellow car reads more than the scale attached to the green car. 5. Two boys throw balls with the same force. The baseball accelerates more than the softball.
  2. 2. Using Newton's Second Law, Force= mass x acceleration, calculate the force in each of the following problems. 6. An orange of mass 0.4 kg falls from a tree with an acceleration of 10 m/s2 . How large is the force acting on the orange? 7. A baseball has a mass of 0.3 kg. A pitcher with a really great arm can give the baseball an acceleration of 300 m/s2 . What is the force acting on the ball? 8. A tennis racket supplies an acceleration to a tennis ball of 700 m/s2 . The ball has a mass of 0.02 kg. What is the force acting on the ball? 9. The flipper on a pinball machine accelerates the pinball at 0.5 m/s2 . The pinball's mass is 0.01 kg. What is the force acting on the ball? Using Newton's Second Law in the form: Acceleration = force/mass, calculate the acceleration in each of these situations. 10. A race car having a mss of 2550 kg is accelerated by a force of 127,500 N. Find acceleration. 11. A 0.10 kg bullet is fired from a gun with an average force of 600 N. What is the acceleration of the bullet in the barrel? 12. A cat with a mass of 4 kg and a weight of 40 N drops to the ground. What is the cat's acceleration? 13. A cyclist and his bike have a combined mass of 200kg. How much acceleration is produced by a force of 1200 N? Newton's Second Law can also be used to calculate the mass, in this form: Mass = force /acceleration. Calculate the mass of these objects and show your work. 14. What is the combined mass of a person on a skateboard if a 1800 N force produces an acceleration of 12 m/s2 . 15. What mass will be accelerated at 5.0 m/s2 by a force of 1750 N? Calculating Weight Using Newton's Second Law Weight is a force. This force causes all objects near the surface of the earth to accelerate at the same rate. Therefore Newton's second law can be used to calculate the weight of an object. Weight = mass x acceleration, acceleration = 9.8 m/s2 . Remember that the unit of weight is the newton (N). 16. An apple has a mass of 1.0 kg. What is its weight? 17. The mass of a weight lifter is 136 kg. How much weight is this?
  3. 3. 18. An automobile has a mass of 1820 kg. What is the weight of the auto? Newton's second law can also be used to calculate the mass of objects if their weight is known. Mass = force/acceleration. 19. A weightlifter lifts a weight of 2000N. What mass did he lift? 20. The weight of a sack of groceries is 250 N. What is its mass? Newton's Third Law In each of the following situations, describe the reaction. 1. A baseball bat exerting a force on a ball is the action. What is the reaction? 2. The tires of a car pushing against the road is the action. What is the reaction? 3. The action is the earth pulling on an apple and making it fall to the ground. What is the reaction? 4. A football player running up the field collides with a player standing at the 50 yard line. The action is the force the moving player exerts on the stationary one. What is the reaction? 5. A tractor pulls on a chain attached to a tree stump. The action is the force the tractor exerts on the stump. What is the reaction?

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