What does wanted friction mean in science?

Frequency of a sound wave? Does frequency depend on mass? What kind of energy does a skydiver falling use? A 1600 kg car is traveling at a speed of 12.5 ms what is the kinetic energy of energy car? How do you get work done if you have given mass and power? What are the two contact forces examples? An unknown sample scatters light and passes through a filter without leaving a residue the sample is most likely a? Why has my grandfather clock's pendulum stopped swinging? Did the Greeks discover particles? What are the two types of waves that make up electromagnetic waves? What electromagnetic spectrum is energy that travels by radiation? What is depolarized light? What are not able to travel through empty space ultraviolet waves or sound waves? How much is 5000 shekels of bronze in pounds? How does the parachute helps an object to fall slowly? How many meters and centimeters are there in 9.81 meters? What did Albert Einstein work as before becoming a physicist? An echo for example wave interaction? How has the consumption of energy per person changed over the last 50 years? Compare how mirrors and lenses affect light rays?

What does wanted friction mean in science?