Why don't you have to make your heart beat?

because ur brain subconsciously signals your heart to do it in order to stay alive

Explanation:

Some muscles in the body are “involuntary”, which means you can't control them. The heart is made of a special involuntary muscle called cardiac muscle, and this muscle is made up of cells called cardiomyocytes (which literally means “heart muscle cells” in Latin)

acceleration = (change in speed) / (time for the change)

change in speed = (20-120)= -100 m/s.

1.5 min = 90 sec

acceleration = -100/90 = -1.11 m/s^2.

we don't care about the 150kg or the 2,500 meters. they don't make any difference.

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the answer is 100. i just did this lesson and got a 100% on it. : )

-fishtank