YOU NEED:
+ A stack of books, 4-6 inches tall
+ A firm ruler (or other long, firm, flat object)
+ A round, heavy object like an orange, paper weight, or ball
MAKE AN INCLINED PLANE:
1. Prop the ruler up on the books so that one end rests on the top of the books and the other on the ground.
2. Use two fingers to pinch the object and lift it to the top of the stack of books.
3. Use two fingers to roll or slide the object up the inclined plane.
Is it easier or more difficult to lift the object th