Explanation:
It is given that,
The volume of a right circular cylindrical, 
We know that the volume of the cylinder is given by :

............(1)
The upper area is given by :



For maximum area, differentiate above equation wrt r such that, we get :



r = 1.83 m
Dividing equation (1) with r such that,



Hence, this is the required solution.
Mechanical energy can have mechanical systems. The only mechanical system in the list is the compressed spring. A car battery and a glowing incandescent lightbulb have electrical energy, a nucleus of atom has potential (internal) energy.
Answer: Physical
Explanation: There are no changes being done to the salt. Think of it this way, if you dissolve the salt in water then boil the water completely, you will have the same salt you started with.
Answer:
<em>The velocity after 12s is 50.4m/s</em>.
Explanation:
<em>In acceleration formula make velocity the </em><em>subject.</em>
<em> acceleration(a) = velocity(</em>v)÷time(t)
<h3><em> </em><em>velocity</em><em> </em><em>(</em><em>v)</em><em> </em><em>=</em><em> </em><em>acceleration</em><em>(</em><em>a)</em><em>×</em><em>t</em><em>ime</em><em>(</em><em>t)</em></h3>
<em>V </em><em>=</em><em> </em><em>4</em><em>.</em><em>2</em><em>m</em><em>/</em><em>s²</em><em>×</em><em>1</em><em>2</em><em>s</em>
<em>V </em><em>=</em><em> </em><em>5</em><em>0</em><em>.</em><em>4</em><em>m</em><em>/</em><em>s</em>
<em>Therefore</em><em> the</em><em> </em><em>velocity</em><em> </em><em>after</em><em> </em><em>1</em><em>2</em><em>s</em><em> </em><em>is </em><em>5</em><em>0</em><em>.</em><em>4</em><em>m</em><em>/</em><em>s.</em>