Study Guide for Forces and Newton s Laws Test- Honors

Transcription

1 Study Guide for Forces and Newton s Laws Test- Honors What is a force? What are the two types of forces? & What is the unit for Force? for mass? for velocity? for acceleration? What does it mean when forces are in equilibrium or balanced? If an object is moving at a constant velocity, what can you say about the forces affecting it? If an object is changing its velocity, what can you say about the forces affecting it? Which object has a greater force of gravity affecting it, bowling ball or basketball? Explain your answer. Draw a force diagram of a 300 kg gorilla hanging from two ropes. What is the tension force on each of the ropes? Tom can pull with a maximum force of 275 N while Teresa can pull with a maximum of 315 N. a. What is the largest amount both of them can pull together? Diagram the answer. b. What is the least amount both of them can pull together? Diagram the answer. c. How is it possible to have a combined force between answers a and b above while still pulling with the maximum amount of force? Diagram the answer. 1

2 Bailey, my dog, pulls on a toy with a force of 16 N toward the south. At the same time, my daughter Lauren pulls on it with a force of 22 N to the west. Calculate the vector sum of the two forces applied to the toy. (Show all formulas, work, answer and units) If the toy is glued to the floor and not moving, with how much force is the glue sticking? A skydiver jumps out of a plane. Draw a force diagram, and x-t, v-t, and a-t graphs. If the mass of the skydiver is 58 kg, what is the amount of air resistance on her when she reaches terminal velocity (falling at a constant speed)? You are pushing a 1.5 kg book across the desk and you are overcoming 0.4 N of friction. How much force is needed to move it at a constant velocity? How much frictional force is needed to slow down a car with a mass of 3000 kg? 2

3 A swing is suspended by two ropes. Joe and Jackie sit together on the swing. The force due to gravity on the swing is 60 N. The force of gravity on Jackie is 460 N and on Joe is 590 N. What is the tension force on both ropes? (Show all formulas, work, answer and units) Joe and Jackie start swinging from side to side and get the swing at a 45 angle. How much tension is on each rope now? (Show all formulas, work, answer and units) On the moon, you find a rock that has a weight of 27 N. How much would it weigh on Earth? (Acceleration moon = 1.6 N/kg) (Show all formulas, work, answer and units) For the blocks below, make the qualitative Force Diagrams. At rest At rest At terminal velocity At rest 3

4 1. Using Newton s First Law, explain why you it is important to always wear your seat belt. 2. What does Newton s Third Law say about two objects that are touching? 3. If you are in a car crash a. which object feels a larger force, your car or the other car? Why? b. Write the action/reaction force pair statements for your car and the other car. 4. If you push your binder across a table a. which feels a larger force, you or your binder? Why? b. Write the action/reaction force pair statements for you and your binder. 5. Write Newton s Second Law in symbols. 6. If you have a 10kg box and a 20 kg box, and you want them to accelerate at the same rate. Which should you push harder and how much harder? 7. You are moving a dresser and a bed. The dresser is full of clothes and is double the mass of the bed. If you push on both pieces of furniture with the same force, which will have a smaller acceleration? 8. You have two mystery objects. You push them with the same force and they have the exact same acceleration. How do their masses compare? (Which one has a larger mass?) 9. An astronaut is in space and floating motionless near her space shuttle. She is not tethered and only has a toolbox and a backpack. a. If she wants to move toward her space shuttle, what can she do to get there? Nothing. There is no way for her to move b. If she wants to move farther from her space shuttle, what can she do to get there? Nothing. There is no way for her to move. 4

5 c. If she is moving at a constant velocity, what can she do to speed up? Nothing. There is no way for her to move. d. If she is moving at a constant velocity, what can she do to slow down? Nothing. There is no way for her to move. 10. Love is in the air! What is the gravitational attraction between you and your crush if one of you is 66 kg, the other is 63 kg, and you are sitting 4 meters apart staring into each other s eyes? 11. Suppose that two objects attract each other with a gravitational force of 16 units. If the distance between the two objects is doubled, what is the new force of attraction between the two objects? 12. Suppose that two objects attract each other with a gravitational force of 16 units. If the mass of both objects was doubled, and if the distance between the objects remained the same, then what would be the new force of attraction between the two objects? 13. The universal of Newton's law of universal gravitation means that a. the amount of gravitational forces is the same for all objects. b. the acceleration caused by gravity is the same for all objects. c. the force of gravity acts between all objects - not just between the Earth and an object, but also between two people. All objects with mass attract. 14. According to Newton's gravitation law, the force of gravitational attraction between a planet and an object located upon the planet's surface depends upon. Choose all that apply. a. the radius of the planet b. the mass of the planet c. the mass of the object d. the volume of the object e. nonsense! None of these variables affect the force of gravity. 15. The more massive that an object is, the (more, less) that the object will be attracted to Earth. 16. The more massive the Earth is, the (more, less) that another object will be attracted to Earth. 17. The greater that Earth's radius is, the (more, less) that another object will be attracted to Earth. 5

6 18. In the mathematical form of Newton's law of universal gravitation ( ), the symbol G stands for. a. gravity b. the acceleration of gravity c. the gravitational constant 19.Force diagrams for four different situations are shown below. The net force is known for each situation. However, the magnitudes of a few of the individual forces are not known. Analyze each situation individually and determine the magnitude of the unknown forces. B C 300 N F A 50 N 75 N 19 N G D 200 N 180 N E H Fnet = 0 N Fnet = 920 N, up Fnet = 63 N, left Fnet = 31 N, right A C D F B E G 20.What kind of force(s) do we see with. H 28 N _ 1. Ropes 2. Soccer balls 3. People 4. Surfaces 3. Shocks 6. Earth 21..Normal force always pushes a. Straight up b. North c. Perpendicular to the surface d. trickery! Normal force doesn t push, it pulls! 6

7 !!!CHALLENGE PROBLEMS!!! 1!!! If the frictional force holding the block in place is 47 N, what is the mass of the block? 35º 2!!! The 350 kg block below is held at a 72 angle. If you were going to buy the rope to hold it, what would be its minimum strength needed? 3!!! If the mass of the Sun is x kg. How close would the earth have to be to the Sun be able to steal a 75 kg person from Earth? 7