Please help me with this

the answer is mixtures.

Explanation:

mixtures can be separated physically. elements like the ones on the periodic table cannot be further broken down. compounds are bonds between two or more elements and can only be broken down chemically.

A pure substance, any compound or element, can't be separated into different atoms by physical methods. A chemical reaction must occur to separate a compound into its different atoms/elements.

a: 45.9 meters

b: 4.29 seconds

step-by-step explanation:

a: h(t)=1/2(-9.8)(3)^2+0(3)+90

h(t)=-4.9(3)^2+90

h(t)=-44.1+90

h(t)=45.9 meters

b: 0=1/2(-9.8)(t^2)+0t+90

0=-4.9t^2+90

-90=-4.9t^2

18.37=t^2

t=4.29 seconds

in the second question, the numbers aren't exact, but they're a close approximation.