Answer: Physical changes only change the appearance of a substance, not its chemical composition. Chemical changes cause a substance to change into an entirely substance with a new chemical formula. Chemical changes are also known as chemical reactions.
Explanation:
C) In the absence of an unbalanced force, an object at rest will stay at rest and an object in motion will stay in motion.
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Answer:
A. -30 N
Explanation:
not sure but if the box isn't moving then the force opposite of Polly would be equal to the force she's exerting.
Answer:
(a) 3.24 w (b) 44.44 ohm
Explanation:
It is given that car draws 0.27 A current so current I = 0.27 A
The system has a voltage of 12 V
(a) Electrical power = voltage ×current 
(b) The resistance is defined as the ratio of voltage and current
So resistance 
Answer:
B. Ecosystem B, because its high species diversity could have resulted from increased competition among its members.
Explanation:
This is because, in the ecosystem with varying level of biodiversity, Ecosystem B has medium level of species diversity found in them with High medium level of habitat diversity which causes increasing competitions among them.
