70. Historically, replacing dirt roads with paved roads reduced friction on vehicles. Replacing paved roads with steel rails reduced friction further. What recent step eliminates rail friction of vehicles?

When the force acting on an object points at least partially in the direction of the motion the work done is considered to be negative

Much of the information taught in earth-space science would not be available if it weren’t for our remote sensing abilities. explain two ways our remote sensing strategies contribute to our knowledge of these topics.

What does the law of conservation of mass state?