<h3><u>Answer and explanation;</u></h3>
- <u>Melting point</u> is defined as the temperature at which solid and liquid phases are in equilibrium. It is the temperature at which a solid changes state from solid to liquid at atmospheric pressure.
- <u>Boiling poin</u>t is the temperature at which the vapour pressure of a liquid is equal to the external pressure. It is the temperature at which a substance changes from a liquid into a gas.
- <u>The flash point </u>of a flammable liquid or volatile liquid is the lowest temperature at which it can form an ignitable mixture in air. At this temperature the vapor may cease to burn when the source of ignition is removed.
Answer:
Before start of slide velocity will be 14.81 m/sec
Explanation:
We have given coefficient of static friction 
Angle of inclination is equal to 


Radius is given r = 28 m
Acceleration due to gravity 
We know that 



So before start of slide velocity will be 14.81 m/sec
velocity = distance / time v= d/t firstly you change 3000 m into km distance D = 3000/1000 = 3 km secondly time t = 21 min using velocity formula v = d/t = 3 km/21min =0.142km/min