Ill. Write True if the sentence is correct. If the sentence is incorrect, change the underlined word or ph make it true. 1 2. 3. Frictional force is greater between smooth surfaces. Frictional force always causes problem. A material used to make surfaces slippery is called parachute Oil and grease are examples of lubricants The more streamlined an object is, the lesser is the air resistance acting on it 4 5​