1. flying a plane (friction between air and plane) 2. ice skating (friction between ice and skate blade) 3. swimming (water & skin) 4. rowing a boat (water and boat)
Dr. Inge discovered the make up of the earths inner core by studying how an earthquakes waves bounced off the core. And Inge Lehmann was studying the waves of a 1929 earthquake when she found them acting inconsistently with solid mantle crust hope it helps you