<span>A pure substance is an element or compound. If it's an element, then it's made of only one kind of atom. If it's a compound, then it's made of only one kind of formula unit. For example, hydrogen (H2) and oxygen (O2) are elements. In pure samples of H2 and O2, you find only one kind of element. H2O is a compound, water. In pure samples of H2O, you find only formula units of H2O (called molecules because H2O is covalent). Neither the components that make up H and O atoms, nor the atoms that make up H2O can be separated by physical means. H2, O2, and H2O are all considered substances. </span>
The greatest percent of mass of the universe is dark matter
Answer:
Time= 6.12*10^4s
mass flow rate m=0.98kg/s
Explanation:
Given
Volume= 60m^3
diamter= 2.5cm= 0.025m
radius= 0.0125m
area A= πr^2
area A= 3.142*0.0125^2
area A= 4.9*10^-4m^2
the velocity of the flow 2m/s
<u>volume flow rate </u>
V=vA
V=2* 4.9*10^-4
V=9.82*10^-4 m^3/s
<u>Time taken to fill the pool</u>
time= volume/volume flow rate
time= 60/9.82*10^-4
time= 6.12*10^4s
<u>Mass flow rate </u>
m= density *volume flow rate
Assuming the density of water to be 997kg/m^3
m= 997*9.82*10^-4
m=0.98kg/s
I looked up the question and got D- a vacuum
Answer:
it is actually very easy & interesting. first write formula of force F=Mass×Acceleration . now see what are the unknowns , mass is known but acceleration is not . so find acceleration, a=velocity/time , but now again we dont know velocity, V= distance/time . subbing in all the values, Force=Mass×(distance/time^2)
Hope it helps if you have any problem feel free to ask.
