Why do trains use steel wheels rather than rubber tires? a) steel wheels provide more grip, making it easier to stop a train.
b) rubber tires don't provide enough friction to allow the train to move.
c) steel wheels increase friction, thus making it easier to move the load.
d) steel wheels reduce friction, thus requiring less force to move the load.

d) the number of neutrons plus the number of protons

a high pressure system is a dense air mass that is usually cooler and drier than the surrounding air. a low pressure system is a less dense air mass that is usually wetter and warmer than the surrounding air.

in general, areas that experience high atmospheric pressure also experience fair weather. low pressure systems can cause the formation of clouds and storms. air usually flows from areas of high pressure to areas of low pressure..