Investigate how friction, a force between two touching surfaces, slows or stops a moving object, and compare friction on different surfaces using a fair test.
Friction is a force created when two surfaces rub against each other, and it always works against motion, slowing a moving object down. Some surfaces make more friction than others: rough surfaces like carpet or sandpaper create a lot of friction, while smooth surfaces like polished tile or ice create much less.
You can test friction with a simple, fair investigation: send the same object down the same ramp onto different surfaces, and measure how far it slides before stopping. A fair test changes only ONE thing, the surface, and keeps everything else, the ramp height, the object, and the push, exactly the same.
Mastery looks like: They can predict which of two surfaces creates more friction and explain the result using a fair test they ran themselves.
Common stumbles: Believing a smooth surface has "no" friction at all, rather than understanding it simply has less friction than a rough one.