D. Kinetic D. none of these C. heat 1. Read each item carefully. Write the letter of 1. The force that acts in the opposite direction of motion when two surfaces come in conta C. Static B. Friction A. Force 2. Friction is a force that acts in an direction of movement. D. west A. similar B. opposite C. parallel 3. You use friction when you leave marks on paper with a pencil "lead". A. static friction B. sliding friction C. rolling friction 4. What does friction produce? D. gravity A. light B. sound 5. Which of these materials do you predict would have the MOST amount of friction. A. Metal B. Tile C. Sand paper D. Denim 6. Which of these is an example of undesirable effect of friction? A. keeping our balance B. forest fire C. running on the street D. writing in notebook 7. Rough surfaces have A. greater friction B. less friction C. same level of friction D. all these are correct 8. Which of the following is an example of friction that is helpful? A. Brakes used on a bike B. Tires from a car on the road C. All are example that are helpful 9. How does friction affect speed? A. more friction decreases speed C. more friction increases speed B. less friction decreases speed D. none of these 10. How can friction be produced? A. reduce the force acting between the 2 surfaces B. reduce the roughness of the 2 surfaces coming in contact C. use wax, grease or oil D. all of the above are ways of reducing friction 11. Which refers to the force that attracts objects toward the earth's surface? A. Force B. Friction C. Gravity D. Kinetic 12. Which refers to the amount of matter in an object? A. friction B. gravity C. force D. mass 13. Which of these is the reason why the moon rotates around the earth? A. friction B. gravity C. heat D. mass 14. What will happen to your weight when you go to the moon? A. Your weight will be gone B. Your weight will increase C. Your weight will decrease 15. What happens to gravitational force as the mass increase? A. increases B. stay the same C. decreases D. not determined 16. Without gravity, we will A. float B. lie down C. disappear D. stay in the ground 17. Which of the following will not change in different gravitational fields? A. weight B. mass C. force D. all these are correct. 18. The law of universal gravitation is credited to whom? A. Einstein B. Newton C. Darwin D. Galileo 19. Why a ball falls to the ground? A. Earth's force of gravity is greater than the ball's, so the ball gets attracted to the ground. B. Earth's force of gravity is less than the ball's, so the ball gets attracted to the ground. C. Both A and B D. None of these is correct. 20. Which statement about gravity is true? A. Gravity causes objects to pull towards one another. B. Gravity causes objects to push away from each other. C. Gravity only takes place between planets D. The moon doesn't have any gravity​