Answer:
Option a
Explanation:
The action of the rapid rubbing of the hands are a result of chemical reaction and responses that takes place inside our body.
When we rub our hands together, that shows the mechanical motion of the body or we can say that while rubbing hands chemical energy gets converted to mechanical energy (here, Kinetic energy).
While rubbing, due to friction, heat is produced and hence we can say that this mechanical energy has transformed to heat energy.
Thus the conversion here is from chemical to mechanical to heat energy.
Answer: 4 ft/s
Explanation:
Given
height of man
speed of person 
height if street light
Let x be the distance between person and street light and y be the length of his shadow
From diagram
as the two triangle ADE and ABC are similar therefore we can say that




differentiate above Equation w.r.t time we get


F=ma
11.6=3.8*a
a=11.6/3.8
a=3.05m/s