Answer:D
A system where matter and energy can not enter or leave the system
Answer:A
Explanation: number that shows the total atomic mass of the substance
The velocity is a vectorial quantity, whereas speed is a scalar quantity, meaning it depends on the direction!
As such, the velocity is changing because the direction is changing.
Answer:

Explanation:
A differential equation that contain a term with di(t)/dt is in a RL circuit. Here we have

where vr is the voltage in the resistance, vi is the voltage in the inductance and vb is the source voltage. But also we have that

where L is the inductance of the circuit, r is the resistance an i is the current. By replacing we have the differential equation

I hope this is useful for you
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Answer:
The cardiovascular system
Explanation: