8 th Grade Science. Directed Reading Packet. Physics. Name: Teacher: Period:

Transcription

1 8 th Grade Science Directed Reading Packet Physics Name: Teacher: Period:

2 Section 1: Distance and Direction Introduction: 1. Define motion. 2. Draw sketches of something in motion in the different areas listed. Motion on Land Motion in Water Motion in Air Motion in Outer Space Frame of Reference: 3. What is a frame of reference? 4. In the school bus example, how does a person at the bus stop use a frame of reference to detect motion? 5. In the school bus example, how does a person on the bus use a frame of reference to detect motion?

3 6. Draw a sketch of an object in motion. Include several frames of references in your sketch. Label the object in motion and the frames of reference. SI Unit for Distance: 7. What is the SI unit for measuring distance? 8. What SI unit is used for measuring short distances? Long distances? 9. Label the following statements as centimeters (cm), meters (m), or kilometers (km). Base your answer on which unit makes the most sense to use to measure the object. Direction: length of a pencil distance from your house to school distance from your 1 st period class to your 2 nd period class your height distance a worm slithers in 2 minutes distance a person walks in 2 minutes distance a car drives on the highway in 2 minutes 10. Why is direction as important as distance in describing motion? Give an example. Summary: Motion is a change of. The perception of motion depends on a person s of. is the length of the route between two points. The SI unit for distance is the. is just as important as distance in describing.

4 Speed: 1. What is the formula used for calculating speed? Section 2: Speed and Velocity 2. Listed below are common ways speed is expressed. Circle the SI (metric) units green and US units red: kilometers per hour (km/h) meters per second (m/s) feet per second (fps) miles per hour (mph) cetimeters per second (cm/s) inches per second (in/s) 3. Calculate the speed of a cyclist that bikes 33 miles in 2.2 hours: 4. Calculate the speed of a rocket that travells 1800 kilometers in 0.12 hours: 5. Draw sketches of something with a low speed and a high speed. Low speed - slow High speed - fast Instantaneous vs. Average Speed: 6. What is the difference between instantaneous speed and average speed. Give an example of each: Distance-Time Graphs: Use the graph to answer the following questions. 7. How many hours did the bike ride last? 8. Calculate the bike riders speed between points A and B. 9. Calculate the bike riders speed between points B and C.

5 10. Calculate the bike riders speed between points C and D. 11. What do you think the bike rider is doing between points E and F? Slope Equals Speed: 12. If the slope of the line on the graph is steep, what can be said about the speed of the object? 13. If the slope of the line on the graph is gentle, what can be said about the speed of the object? 14. If the slope of the line on the graph is straight, what can be said about the speed of the object? 15. If the slope of the line on the graph is curved, what can be said about the speed of the object? 16. If the slope of the line on the graph is horizontal, what can be said about the speed of the object? Velocity: 17. How is velocity different than speed? 18. Circle the measurements for speed red and the measurements for velocity green: 85 km/hr South 27.5 m/s 84 fps upward 13 cm/s 66 mph 17 in/s East 45 cm/s NW 166 m/min Summary: is a measure of how fast or slow something moves. It depends on the traveled and how it takes to travel that distance. The average speed of an object is calculated as the change in divided by the change in. is a measure of both speed and. Velocity changes with a change in, a change in, or both.

6 Introduction: 1. What is the physics defintion of accleration? Section 3: Acceleration Defining Acceleration: 2. What two factors of an object s motion affect the accelearion of the object? 3. Is decrease in speed accleration? Explain. 4. Draw three examples of acceleration: Increasing Speed Decreasing Speed Changing Direction 5. Describe times while riding in a car that you can feel acceleration. 6. Describe times while riding in a car that you can NOT feel acceleration.

7 Calculating Acceleration: 7. What is the formula used to calculate the acceleration of an object? 8. Review the examples in the flexbook for calculating acceleration, then try these problems. A. Noah is riding his Ripstick and increases his velocity from 1 m/s to 7 m/s in 2 seconds. What is Noah s acceleration? Show work. B. Brooke is riding her favorite roller coaster. At the bottom of the first hill she is going 100 km/hr. Five seconds later her velocity slows to 25 km/hr. What is Brooke s acceleration? Show work. C. Silas is on the school bus coming to Tohickon. The bus is traveling 8 m/s as it heads down Old Easton Road. 10 seconds later the velocity is still 8 m/s. Calculate Silas acceleration. Show work. Velocity-Time Graphs: 9. Review the example of the velocity-time graphs in the Flexbook. Then answer the questions using the graph. Use a green colored pencil to highlight the line(s) on graph when the object shows positive acceleration. Use a red colored pencil to highlight the line(s) on graph when the object shows negative acceleration (deceleration) Use a yellow colored pencil to highlight the line(s) on graph when the object shows zero acceleration. Summary: is a measure of the change in velocity of a moving object. It shows how quickly changes and whether the change is or. It may reflect a change in speed, a change in direction, or. To calculate acceleration without a change in direction, divide the change in by the change in. The of a velocity-time graph represents.

8 Introduction: 1. Check all statements below that are true: Defining Force: 2. Define force. Section 4: What is Force? Any time the motion of an object changes, a force has been applied. Force can cause a stationary object to start moving. Force can cause a moving object to accelerate. Force can cause a object to change speed, direction or both. The strength of the force and the mass of the object determine the object s change in motion. 3. Draw three examples of applied forces. Applied Force 1 Applied Force 2 Applied Force 3 SI Unit of Force: 4. What is the SI unit of force? 5. How much force is 1 netwon? Combining Forces: 6. What is net force? 7. Describe the forces acting on the book pictured.

9 Forces Acting in Opposite Directions: 8. How do you calculate net force when forces are acting in opposite directions? 9. Calculate the net force in the picture at right. Forces Acting in the Same Directions: 10. How do you calculate net force when forces are acting in the same direction? 11. Calculate the net force in the picture at right. You Try It! 25 N 20 N 12. Calculate the net force and the direction the ball travels in the picture at left. 75 N 125 N 13. Use colored pencils to draw your own examples of forces acting in same and opposite directions. Force Acting in Opposite Directions Force Acting in Same Direction Summary: Force is a or acting on an object. Examples of force include and. The SI unit of force is the (N). The combined forces acting on an object are called the force. When forces act in directions, they are subtracted to yield the net force. When they act in the direction, they are added to yield the net force.

10 What is Friction? 1. Define friction. Section 5: Friction 2. Draw original examples of helpful fiction and harmful friction. Example of Helpful Friction Example of Harmful Friction Why Friction Occurs: 3. Describe why friction occurs. Be sure to include why smooth surfaces create friction. Factors that Affect Friction 4. Factors that affects the amount of friction are the roughness of surfaces, surface area of objects, and the weight of the object. Draw some original examples of the factors that affect friction. rough surface lots of friction large surface area - lots of friction heavy weight - lots of friction smooth surface little friction small surface area little friction light weight little friction

11 Friction Produces Heat: 5. Explain why friction produces heat. Be sure to mention molecules in your answer. 6. How can friction between objects be reduced? Types of Friction: 7. Draw examples of the four types of friction. Try to think of something original. Example of Static Friction Example of Sliding Friction Example of Rolling Friction Example of Fluid Friction 8. What is air resistance? Summary: Friction is a that motion between two surfaces that are touching. Friction occurs because no surface is perfectly. Friction is greater when objects have surfaces, have more surface that is touching, or are so they press together with greater force. Types of friction include friction, friction, friction, and friction. Fluid friction with air is called air.

12 Section 6: Gravity Defining Gravity: 1. What is gravity? 2. Do all objects exert a gravitaitonal force? What about something small like a grain of sand? 3. How is gravity different than friction? Earth s Gravity: 4. Use colored pencils to draw two examples that show the Earth s gravitional force. Example 1 Example 2 Gravity and Weight: 5. Define weight. 6. Describe the SI unit for measuring weight.

13 7. What is the difference between mass and weight? Give an example. 8. What device is used to measure weight? What device do you think is used to measure mass? Newton s Law of Universal Gravitation: 9. Describe Newton s Law of Universal Graviation. 10. Why did Newton s description of gravity have such a big impact? Factors that Influence the Strength of Gravity: 11. How does the mass of the object affect gravitational force? 12. How does the distance between objects affect graviational force? 13. Use colored pencils to draw original examples of the factors that affect gravitational force. large mass lots of gravity great distance between objects little gravity small mass little gravity small distance between objects more gravity

14 Accleration Due to Gravity: 14. Explain the acceleration of a falling object. 15. Why does a bowling ball reach the ground the same time as a basketball when dropped? 16. Why does leaf hit the ground later than an acorn dropped at the same time? 17. An object is dropped off a cliff. A picture is taken each second as it falls. On the diagram at right, write the velocity of the dropped object at each point of its descent. Projectile Motion: 18. Explain why an object thrown horizontally will travel in a curved path toward the Earth s surface. 19. The bow is aimed at the center of the target below. Draw a line of the path that the arrow will travel.

15 20. Draw original examples of the projectile motion in action. Projectile motion example 1 Projectile motion example 2 Orbital Motion: 21. Explain why the moon stays in orbit around the Earth. 22. Draw a satellite and orbit around the Earth. Label the accelertion and velocity on the diagram. Summary: Gravity is traditionally defined as a force of between two masses. Weight measures the of gravity and is expressed in (N). According to Newton s law of gravitation, gravity is a force of attraction between objects in the universe, and the strength of gravity depends on the of the objects and the between them. Gravity causes falling objects to at 9.8 m/s 2. Gravity also causes motion and motion.

16 Force and Motion: 1. State Newton s first law of motion. Section 7: Newton s First Law 2. Draw original examples how Newton s first law can be observed. An object at rest, remains at rest. An object in motion, remains in motion. Inertia: 3. Newton s first law is also called the law of inertia. Define inertia. 4. Describe an example (not from the Flexbook) of how you personally experience inertia during the day. Inertia and Mass: 5. How is the inertia of an object related to its mass? Overcoming Inertia: 6. A non-moving soccer ball is kicked and flies through the air, bounces on the grass and rolls to a stop. Describe how inertia was overcome to get the ball in motion and also how inertia was overcome for the ball to come to a stop again. Summary: Newton s first law of motion states that an object s motion will not change unless an force acts on the object. If the object is at, it will stay at. If the object is in, it will stay in. is the tendency of an object to a change in motion. The inertia of an object depends on its. Objects with mass have inertia. To overcome inertia, an force must be applied to an object.

17 Acceleration, Force, and Mass: Section 8: Newton s Second Law 1. What two factors did Isaac Newton determine affect the acceleration of an object? 2. State Newton s second law of motion. Include the equation. Direct and Inverse Relationships: 3. Draw original examples of the two aspects of Newton s second law. The greater the force applied, the more the object will accelerate. The greater the mass of the object, the less it will accelerate. Calculating Accleration: 4. Use the formula for Newton s second law of motion to calculate acceleration in the examples below. Remember 1 Newton is equal to 1 kg-m/s 2 F = 100 N M = 50 kg 5. Find the acceleration of the sled when one dog is pulling it. F = 200 N M = 50 kg 6. Find the acceleration of the sled when two dogs are pulling it. 7. What would be the acceleration of the sled if two dogs were pulling it, but the mass was reduced to 25kg? Summary: Newton s second law of motion states that the of an object equals the net acting on the object divided by the object s.

18 Sections 9, 10, 11: Newton s Third Law and Momentum Action and Reaction: 1. What is Newton s Third Law of motion? 2. How does the diagram at right demonstrate Newton s Third Law? 3. Why don t action and reactions cancel each other out, like balanced forces? Explain using an example. 4. Draw two original examples of Newton s third law being observed. Momentum: 5. Write the formula to calculate momentum: 6. Calculate the momentum of the car and truck below:

19 Conservation of Momentum: 7. Explain the law of conservation of momentum. 8. How can you tell momentum has been conserved in the collision pictured below? Summary: Newton s third law of motion states that every has and equal and opposite. is a property of a moving object that makes it hard to. It equals the object s times its. When an action and reaction occur, may be transferred from one object to, but their combined remains the same. This is the law of of.