When standing on a flat surface physics is involved. The polar bear in the picture is experiencing physics. The polar bear is putting a force of gravity on the ice while the normal force of the ice is holding the polar bear up. If the ice gets weaker and to the point where it doesn't have enough normal force, the polar bear will break through the ice. It will break through because there isn't enough normal force to support the polar bears gravitational force. This is an example of Newton's second law.