Skills Worksheet Directed Reading B Section: Friction: A Force That Opposes Motion 1. What unbalanced force causes a ball to stop rolling? a. friction opposing motion b. gravity pulling down c. the ground pushing up d. the force of the throw or kick THE SOURCE OF FRICTION 2. What two things affect the amount of friction? a. energy and heat b. energy and surface roughness c. force and heat d. force and surface roughness The Effect of Force on Friction 3. Why does sliding large books take more force than sliding small books? a. The large books have more surface roughness. b. The large books have more weight pushing down. c. The large books have less air. d. The large books have less heat. The Effect of Rougher Surfaces on Friction 4. Why does dry pavement create more friction than ice does? a. Dry pavement has more heat. b. Dry pavement has less heat. c. Dry pavement is smoother. d. Dry pavement is rougher. Holt Science and Technology 22 Matter in Motion
5. What happens to the road friction when a road gets rougher? a. There is no friction. b. The friction is less. c. The friction is greater. d. The amount of friction stays the same. TYPES OF FRICTION Kinetic Friction 6. Which of these examples shows sliding kinetic friction? a. pushing a desk across the floor b. pushing a desk that will not move c. a bicycle on a sidewalk d. an airplane flying 7. Which of these examples shows rolling kinetic friction? a. pushing a desk across the floor b. pushing a desk that will not move c. a bicycle moving on a sidewalk d. an airplane flying Static Friction 8. Which of these examples shows static friction? a. pushing a desk across the floor b. pushing a desk that will not move c. a bicycle on a level sidewalk d. an airplane flying Holt Science and Technology 23 Matter in Motion
9. Which kind of friction keeps a heavy object from moving when you push it? a. rolling kinetic friction b. sliding kinetic friction d. surface friction 10. Which type of friction occurs once an object is moving? a. no friction b. kinetic friction d. surface friction Read the description. Then, draw a line from the dot next to each description to the matching word. 11. a hockey puck moving on ice 12. a crate resting on a ramp 13. a car racing in competition a. sliding kinetic friction b. rolling kinetic friction Holt Science and Technology 24 Matter in Motion
Use the figures below to answer questions 14, 15, and 16. Circle the letter of the best answer for each question. Block Force applied Static friction Force applied Kinetic friction Table (A) (B) (C) 14. Look at Figure A above. Why does the block not move? a. no force is being applied b. force of friction c. surface friction d. kinetic friction 15. Look at Figure B above. The block does not move. What force keeps the block from moving? a. rolling kinetic friction b. sliding kinetic friction d. kinetic friction 16. Look at the Figure C above. The block is moving. What force acts against the block s motion? a. static friction b. sliding kinetic friction c. rolling kinetic friction d. gravity Holt Science and Technology 25 Matter in Motion
FRICTION: HARMFUL AND HELPFUL 17. What would happen if you tried to walk without friction? a. you would slip and fall b. you would get lost c. you would change direction d. you would go slower Some Ways to Reduce Friction 18. Which of the following is a way to reduce friction? a. Wear textured batting gloves. b. Press harder while sanding wood. c. Increase the force between two surfaces. d. Place ball bearings between wheels and axles. Some Ways to Increase Friction 19. Which of the following is a way to increase friction? a. Use a lubricant. b. Make rubbing surfaces smoother. c. Push surfaces together. d. Switch sliding kinetic friction to rolling kinetic friction. Holt Science and Technology 26 Matter in Motion
TEACHER RESOURCE PAGE 10. direction 11. direction 12. same 13. opposite 14. acceleration 15. accelerating 16. increasing 17. decreasing 18. C 19. B 20. A 21. D SECTION: WHAT IS A FORCE? 1. force 2. motion 3. newton 4. B 5. C 6. B 7. D 8. A 9. A 10. D 11. A 12. B 13. B SECTION: FRICTION: A FORCE THAT OPPOSES MOTION 1. A 2. D 3. B 4. D 5. C 6. A 7. C 8. B 9. C 10. B 11. A 12. C 13. B 14. A 15. C 16. B 17. A 18. A 19. B SECTION: GRAVITY: A FORCE OF ATTRACTION 1. A 2. A 3. C 4. D 5. B 6. A 7. B 8. Earth 9. planet 10. force 11. gravitation 12. C 13. D 14. A 15. B 16. C 17. D 18. B 19. D 20. A 21. B Vocabulary and Section Summary SECTION: MEASURING MOTION 1. motion: an object s change in position relative to a reference point 2. speed: the distance traveled divided by the time interval during which the motion occurred 3. velocity: the speed of an object in a particular direction 4. acceleration: the rate at which velocity changes over time; an object accelerates if its speed, direction, or both change SECTION: WHAT IS A FORCE? 1. force: a push or a pull exerted on an object in order to change the motion of the object; force has size and direction 2. newton: the SI unit for force (symbol, N) 3. net force: the combination of all of the forces acting on an object Holt Science and Technology 114 Matter in Motion