III. True or False. Write I if the statement is correct and F if it is incorrect.
11. Friction converts some energy into heat.
12. Lubricants like oil, wax causes greater friction.
13. Rough surfaces produce greater friction than smooth surfaces.
14. The strenght of the force of friction depends on the type of surfaces and how hard the surfaces push together,
15. The Principle of Gravity was discovered by Sir Isaac Newton.
16. Gravity is the force between any two objects in the universe.
17. The farther two objects are from each other, the smaller the gravitational pull will be between them.
18. The gravitational force exerted by the earth on an object is not equivalent to the object's weight,
19. The greater mass an object has, the greater its weight.
20. Gravity causes the object to fall towartds the earth.​