Answer:
we can not use the suns energy too effectively in power cells and with human power we can generate more energy
Answer: 150 m
Explanation:
velocity = 22 m/s
t = 6.8 s
velocity = 
distance = velocity × time
= 22 × 6.8
= 149.6 m
≈ 150 m
option C
Answer:

is time required to heat to boiling point form initial temperature.
Explanation:
Given:
initial temperature of water, 
time taken to vapourize half a liter of water, 
desity of water, 
So, the givne mass of water, 
enthalpy of vaporization of water, 
specific heat of water, 
Amount of heat required to raise the temperature of given water mass to 100°C:



Now the amount of heat required to vaporize 0.5 kg of water:

where:
mass of water vaporized due to boiling


Now the power rating of the boiler:



Now the time required to heat to boiling point form initial temperature:


This is hard sorry but I need to anwser