Skills Worksheet Vocabulary and Section Summary A Measuring Motion VOCABULARY In your own words, write a definition of the following terms in the space provided. 1. motion 2. average speed 3. velocity 4. acceleration SECTION SUMMARY Read the following section summary. An object is in motion if it changes position over time in relation to a reference point. Average speed is the total distance that an object travels divided by the total time that the object takes to travel that distance. Speed can be shown on a graph of position versus time. Velocity is speed as well as the direction of motion. The velocity of an object changes if the object s speed, direction, or both change. Acceleration is the rate at which velocity changes. An object can accelerate by changing speed, direction, or both. Acceleration can be shown on a graph of speed versus time. Holt California Physical Science 19 Matter in Motion
Skills Worksheet Vocabulary and Section Summary A What Is a Force? VOCABULARY In your own words, write a definition of the following terms in the space provided. 1. force 2. newton 3. net force SECTION SUMMARY Read the following section summary. A force is a push or a pull. Forces have magnitude and direction and are expressed in newtons. Forces always act on objects. The combined effect of the forces acting on an object is the net force. Forces acting in the same direction are added. Forces acting in opposite directions are subtracted. Balanced forces cause no change in motion. The forces on a static object are balanced and can be identified. Unbalanced forces cause a change in velocity. Holt California Physical Science 20 Matter in Motion
Skills Worksheet Vocabulary and Section Summary A Friction: A Force That Opposes Motion VOCABULARY In your own words, write a definition of the following term in the space provided. 1. friction SECTION SUMMARY Read the following section summary. Friction is a force that acts in a direction opposite to the direction of motion. Factors that affect the magnitude of friction include the force pushing the surfaces together and the materials that make up the surfaces. Kinetic friction is a force that, when unbalanced, can change the velocity of a moving object. Static friction can balance other forces and can prevent changes in motion. Friction can be helpful or harmful. Holt California Physical Science 21 Matter in Motion
Skills Worksheet Chapter Review USING VOCABULARY 1. Academic Vocabulary In the sentence The speed of an object can vary, what does the word vary mean? Complete each of the following sentences by choosing the correct term from the word bank. friction acceleration average speed velocity net force newton 2. opposes motion between surfaces that are touching. 3. The is the unit of force. 4. is determined by combining forces. 5. is the total distance traveled divided by the total time elapsed. 6. may be a change in speed or a change in direction. UNDERSTANDING CONCEPTS Multiple Choice 7. Which of the following changes can happen when the forces on an object are unbalanced? a. The object speeds up. b. The object slows down. c. The object changes direction. d. All of the above 8. Which of the following is NOT an example of a change in velocity? a. a person jogging at 3 m/s along a winding path b. a car stopping at a stop sign c. a cheetah running 27 m/s east d. a plane taking off 9. How do you know if the forces on an object are balanced? a. The object speeds up. b. The object slows down. c. The object s motion does not change. d. The object s direction of motion does not change. Holt California Physical Science 39 Matter in Motion
Chapter Review continued Short Answer 10. Describing Describe how to use a reference point and a set of reference directions to define the position of an object. 11. Justifying How is it possible to be accelerating and traveling at a constant speed? 12. Analyzing Why do you think that arrows of varying lengths are used to represent forces? (Hint: Think about magnitude and direction.) 13. Summarizing Describe how to find the cumulative effect of two or more forces acting on an object. 14. Applying How can you increase the magnitude of friction between two surfaces? How can you decrease the magnitude of friction? Holt California Physical Science 40 Matter in Motion
Chapter Review continued MATH SKILLS 26. Using Equations What is the average speed of a kangaroo that hops 60 m in 5 s? Show your work below. 27. Using Equations Find the distance traveled by a baseball in 1.7 s if the baseball s average speed is 22.4 m/s. Show your work below. 28. Using Equations A car left Sacramento, California, and traveled at an average speed of 95 km/h to Redding, California. The distance between the two cities is 260 km. How many hours was the car traveling? Show your work below. CHALLENGE 29. Applying Concepts Describe the motion of a bouncing ball. Are unbalanced forces acting on the ball? Explain your answer. Holt California Physical Science 45 Matter in Motion
Chapter Review continued INTERPRETING GRAPHICS Use the image below to answer the next three questions. Position (m) Movement of a Cat 8 7 6 5 4 3 2 1 0 0 1 2 3 4 5 6 7 8 9 10 Time (s) 15. Concluding During which period of time is the cat standing still? 16. Analyzing When is the cat moving with the greatest speed? 17. Describing Describe the motion of the cat during the last 3 s. WRITING SKILLS 18. Creative Writing Write a short story about a group of friends who must work together to overcome friction in three different situations. Be sure to identify the kind of friction involved in each situation. Holt California Physical Science 41 Matter in Motion
Chapter Review continued 20. Analyzing Ideas Imagine that you walk from your home to a store that is five blocks away. Do you think that your speed will be constant or will vary along the path that you travel? Explain your answer. 21. Identifying Relationships Explain why airplane pilots should know wind velocity and not just wind speed during a flight. 22. Applying Concepts Can balanced forces act on a moving object? Explain your answer, and describe the motion of the object. 23. Analyzing Ideas A rock rolls halfway down a hill and then comes to a stop. What caused the rock to stop moving? Identify two forces acting on the static rock. INTERPRETING GRAPHICS Use the image below to answer the next question. Acceleration of a Car Speed (m/s) 24 20 16 12 8 4 0 0 1 2 3 4 5 6 7 8 9 10 Time (s) 24. Evaluating Data Does the graph show positive acceleration or negative acceleration? Explain your answer. Holt California Physical Science 43 Matter in Motion