
Where r is the radius of balloon.
Here mass of woman = 68 kg
Mass of air displaced by a balloon with volume V = 1.29*V
Mass of helium inside balloon = 0.178*V
Total mass to be lifted by balloon = 68 +0.178*V
Buoyant force = 1.29V-0.178V=1.112V
So we have 1.112 V = 68+ 0.178*V
0.934 V = 68
V = 72.81 
\frac{4}{3} \pi r^{3}[/tex]= 72.81
r = 2.59 m
So radius of helium balloon = 2.59 m
If the resistance of the Air is ignored, we can use the theory given by Galileo in which he warned that the thermal velocity of a body in free fall was given by

Where
g = Gravitational acceleration
t = time
As we can see the speed of objects in free fall is indifferent to the position that is launched (as long as the resistance of the air is ignored) or its mass.
Both bodies will end with the same thermal speed.
Option c) 1.5 V
Explanation:
<em>As the circuit is build in series first we will find the current passing through the complete circuit. Current stays the same in each element is the series cirucuit, however, the voltage is different.</em>
Voltage is given by the following formula:
V = IR
<em>Because we have to find current through whole circuit, we will first find resistance of the whole circuit.</em>
Equivalent Resistance R(eq): R1 + R2 = 60 + 60 = 120 ohm
Current passing through whole circuit be:
= 0.025
Now we will find out the voltage between C and D:
Current stays the same in series circuit: I = 0.025 c
Resistance between C and D is, R = 60 ohm
Voltage becomes, V = IR = 0.025 * 60 = 1.5 V