Which is an indication that a chemical change to a substance has occurred?
a.
it changes shape.
b.
new substances are formed.
c.
energy is used or given off.
d.
both b and c

Alightning strike consists of charge moving from a cloud to the ground . in one particular case, the electrons in a lightning strike are confined to travel within a radius of 1.5 m and to move at a speed of 5.0 x 10 m/s. if the density of electrons in the strike is 10'15 electrons/m what current is carried by the lightning ?

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Acar moves at 12m/s and coasts up a hill with a uniform acceleration of -1.6m/s2. how far has it traveled after 6.0s?