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Name______________________________________ Period ________ Date___________________ Unit 2 Study Guide 1. What is a reference point? A reference point is a place or object used for comparison to determine if something is in motion. 2. What are some examples of descriptions of direction? Up, down, left, right, east, west, north, south 3. What is the difference between speed and velocity? Speed is a measure of distance over time. Velocity is distance over time in a certain direction. 4. How is average speed calculated? Average speed is total distance divided by total time. 5. How is acceleration calculated? Acceleration is a change in speed over time: πππππ π£ππππππ‘π¦ β ππππ‘πππ π£ππππππ‘π¦ π‘πππ Acceleration always involves two measurements of time because it is a measure of a change in velocity (distance over time) over time. A horizontal line on a distance or position over time graph means that the object is at rest (stopped). 6. Why does acceleration always involve two measurements of time? 7. What does a horizontal line on a distance or position over time graph mean? 8. What does a horizontal line on a velocity or speed over time graph mean? 9. What is a force? A horizontal line on a velocity or speed over time graph means that the object is moving at a certain speed. A force is a push or a pull. 10. What is the relationship between force and acceleration? The more force put on an object, the more it will accelerate. The object will move in the same direction. 11. How do you find the net force on an object if two forces are acting in the same direction? 12. How do you find the net force on an object if two forces are acting in opposite directions? If two or more forces are acting on an object in the same direction, you find the net force by adding the forces together. If two or more forces are acting on an object in opposite directions, you find the net force by subtracting the forces. The object will move in the direction of the greater force. 13. Describe the motion of a skydiver The skydiver will be moving at a constant velocity when he who reaches terminal velocity. (page reaches terminal velocity. This happens when the force of air 152) resistance is equal in magnitude and opposite in direction to the force of gravity. 14. What force is demonstrated by the tablecloth trick? Inertia is demonstrated by the magicianβs tablecloth trick. The objectsβ inertia causes them to stay on the table when the cloth is quickly removed. Name______________________________________ Period ________ Date___________________ 15. What is inertia? Inertia is the resistance to a change in motion. 16. What is the relationship between mass and inertia? 17. What is gravity? The more mass an object has, the more inertia it will have. 18. What two factors influence gravity? The strength of the gravitational force between two objects depends on two factors, mass and distance. 19. Why would you be able to jump higher on the moon than on Earth? You would be able to jump higher on the moon than Earth because the moonβs mass is much less than that of Earth, thus the moon exerts less gravitational pull on a body. 20. What is friction? Friction is a force that opposes motion between two surfaces that are in contact with each other. 21. What are two ways to increase friction? Friction can be increased by increasing pressure or by creating a rougher or more adhesive surface. 22. What force is air resistance a type of? Air resistance is a type of friction. Gravity is a force of attraction between objects due to their masses. 23. Name and describe the six simple machines. a. wedge two inclined planes placed back-to-back and used to split or lift objects b. wheel and axle a wheel with a rod running through the wheel c. pulley a grooved wheel with a chain or rope wrapped in the groove d. inclined plane a flat slanted surface that makes it easier to move an object up a distance e. lever a bar that turns on a point f. screw an inclined plane wound around a cylinder or a cone 24. When referring to a simple machine, what is the load? The load is a force or object which must be overcome by the machine. Name______________________________________ Period ________ Date___________________ 25. What is a fulcrum? The point on which a lever pivots is called a fulcrum. 26. What is mechanical advantage? Mechanical advantage is the number of times a machine increases the input force. 27. What is mechanical efficiency? Mechanical efficiency is the ratio of output work to input work. The formula is work output/work input x 100 and is given as a percentage. 28. What is the work done on a machine? The work done on a machine is called work input. 29. What is the work done by a machine? The work done by a machine is called work output. 30. What is the purpose of a machine? The purpose of a machine is to make work easier. 31. How can you increase the mechanical advantage of an inclined plane? 32. How can you increase the mechanical advantage of a lever? You can increase the mechanical advantage of an inclined plane by increasing the length of the ramp. You can increase the mechanical advantage of a lever by moving the fulcrum closer to the load. 34. Calculate the overall average speed. 10 m / 6 sec = 1.67 meters per second Distance (m) 33. Label the diagram: (1) most potential energy (2) least potential energy (3) most kinetic energy (4) least kinetic energy 15 10 5 0 0 2 4 Time (sec) 6 35. Calculate the speed of the object for each leg of the journey. 0 β 2 = 1 meter per second 2 β 4 = 2 meters per second Distance (m) Name______________________________________ Period ________ Date___________________ 15 10 5 0 0 4 β 6 = 1 meter per second 2 4 6 Time (sec) Distance (Km) 36. Write a story to match the graph. 140 120 100 80 60 40 20 0 12 0 β 2 = .25 m/s/s 2 β 4 = .5 m/s/s 14 15 Time (hr) 16 17 6 Speed (m/s) 37. What is the acceleration of the object for each leg of the graph? 13 4 2 0 4 β 6 = 1.75 m/s/s 0 2 4 6 Time (sec) 38. Describe the difference between a speed and acceleration graph. Speed is distance divided by time. Acceleration is speed divided by time. Acceleration represents a change in speed, direction or both. 39. State Newtonβs 1st Law of Motion and give a real example. An object at rest will stay at rest, and an object in motion will continue in motion in a straight line unless acted on by an outside force. 40. State Newtonβs 2nd Law of Motion and give a real example. The tablecloth trick is an example. Force is equal to mass times acceleration. Itβs harder for a big truck to stop than it is for a small car. Name______________________________________ Period ________ Date___________________ 41. State Newtonβs 3rd Law of Motion and give a real example. 42. Calculate: Net force______12N_____________ Direction of movement right 43. Calculate: Net force___3N Direction of movement__ right For every action, there is an equal and opposite reaction. Rockets being shot into space. The exhaust pushing out produces an equal and opposite for pushing back up.