Explain how a thumbtack is designed so that you do not have to use a lot of force to push it through paper or the surface of a bulletin board.

Well, for starters, the end of the thumbtack is sharp, so it can pierce things easily.

Also, paper and bulletin boards are easy to penetrate.

And the thumbtack's point is slippery so it doesn't cause a lot of friction.

And that's why you don't have to use much force to pin something to a board.

Its like a needle the tip percies through the piece of paper as it glides through it

Liquid. good luck : )