A force, such as friction, that operates opposite the direction of motion of a body and tends to prevent or slow down the body's motion. A measure of the degree to which a substance impedes the flow of electric current induced by a voltage. Resistance is measured in ohms.
What is a tornado? A tornado is a violent rotating column of air extending from a thunderstorm to the ground. The most violent tornadoes are capable of tremendous destruction with wind speeds of up to 300 mph. They can destroy large buildings, uproot trees and hurl vehicles hundreds of yards. They can also drive straw into trees.
A: Tornadoes happen when warm, moist air masses and cold, dry air masses collide to cause large thunderstorms. Not all thunderstorms produce tornadoes, and scientists are not certain which factors are directly responsible for their formation. They do know that in many cases, horizontal spinning movements in the air can be lifted vertically.