A student on her way to school walks eastward in a straight line 20.0 meters towards the bus stop, but realizes she dropped her
physics notebook along the way and turns around to retrace her steps. She has traveled back 18.0 meters before finding it and then runs the remaining 45.0 meters due east to the bus stop. What is her total displacement? What is her total distance traveled?
Engineers have designed experimental cars that use liquid hydrogen for fuel instead of gasoline. this is an example of Substitution.
Substitution is the process where one thing replaces other for a particular purpose. here liquid hydrogen is replacing the gasoline for fuel in car. hence the correct word to fill is Substitution.