This attraction occurs from adhesion, also known as adsorption <span />
Explanation:
Mass of the wheel, m = 49 kg
Radius of the hoop, r = 0.73 m
Initial angular speed of the wheel, 
Final angular speed of the wheel, 
Time, t = 22 s
(a) If I is the moment of inertia of the hoop. It is equal to,



We know that the work done is equal to change in kinetic energy.



W = -1858.05 Joules
(b) Let P is the average power. It is given by :


P =84.45 watts
Hence, this is the required solution.
Voltage = current x resistance
since R is doubled, current must reduce by half.
So,
new current = 120/2 = 60mA
<span>1.0 gram (g) of electrons would contain 10^27 electrons
Electrons have an electric charge of −1.602×10−19 coulomb
so total charge of 1 g electrons = -1.602 x 10^-19 x 10^27 = -1.602 x 10^8</span>
I think answer is A. The Brightness of a Star