Answer:
very thick cloth or something maybe wool
Explanation:
Answer: velocity divided by frequency
Explanation: wave speed or velocity measured in meters per second divided by frequency of wave measured in hz
W=mgh
W=(6)(9.8)(4)
W= 235.2J
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:


That you have thrown a ball with kinetic energy upwards at an increasing velocity rate