A stone is thrown upwards with an initial velocity of 25 m/s at an angle of 30^0 to the ground. Without any calculations, state what the stone's vertical velocity will be when it again reaches ground level.

Explanation:

The vertical component of the velocity of stone = 25 sin 30 = 12.5 m/s .

Horizontal component = 25 cos 30 = 21.65 m/s

After the throw , the body will go upwards with reducing velocity  and at top position , its velocity becomes zero . Again it comes down and its velocity gains . When it reaches the surface , it regains its earlier velocity which was in the beginning of the throw that is 25 sin30 but in downward direction .

So its vertical velocity when it reaches the ground will be 25 sin 30 = 12.5 m/s in downward direction.

-first use of geothermal energy occurred more than 10,000 years ago in north america by american paleo-indians

-the first industrial use of geothermal energy began near pisa, italy in late 18th century

-in 1904, italian scientist piero ginori conti invented the first geothermal electric power plant in which steam was used to generate the power

-with the above experiment, the first geothermal plant in usa started in 1922 with a capacity of 250 kilowatts

-however, in 1946 first ground-source geothermal heat pump installed at commonwealth building in portland, oregon

-during the 1960’s, pacific gas and electric began operation of first large scale geothermal power plant in san francisco, producing 11 megawatts

-in 1973, when oil crisis began many countries began looking for renewable energy sources and by 1980’s geothermal heat pumps (ghp) started gaining popularity in order to reduce heating and cooling costs

-as effect of climate change started showing results, governments of various countries joined hands to fight against it, for which kyoto protocol was signed in japan in 1997, laid out emission targets for rich countries and required that they transfer funds and technology to developing countries, 184 countries have ratified it

hope this

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