A chemist, a physicist, and a chemical engineer are rafting down a river. They crash the raft onto the bank. They have a supply of canned goods but no can opener.

The chemist tries to erode the can. That doesn’t work.

The physicist uses his glasses to focus the sunlight to burn a hole in the can. That doesn’t work either.

The chemical engineer stands up and proclaims: “I’ve got it! Assume the can is open!”  Engineering.com