The acceleration due to gravity on the earth’s surface is about 9.8m/sec^2. a) W
ID: 1353216 • Letter: T
Question
The acceleration due to gravity on the earth’s surface is about 9.8m/sec^2.
a) What is the force of gravity on a 1-kg mass?
b) How much mechanical energy could be obtained by fully harnessing the downward movement of a 1-kg mass through a distance of 58 m (the height of Niagara Falls)?
c) How much thermal energy would be produced if the mass were allowed to fall freely through this distance?
d) If the mass consisted of water and all the thermal energy were absorbed by the water, How much would the temperature of the water rise?
Explanation / Answer
1) Force of gravity = m*g
= 1*9.8
= 9.8 N
2) mechanical energy obtained = m*g*h
= 1*9.8*58
= 568.4 J
3) Apply conservation of energy,
thermal energy produced = loss of mehnical energy
= 568.4 J
4) Apply, loss of mechincal energy = gain in thermal energy
m*g*h = m*c*dT (here c is specific heat of water, dT is the increse in temperature)
dT = g*h/(c)
= 9.8*58/4186
= 0.1358 degrees celsius
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