(a) Use of hydrogen fusion to supply energy is a dream that may be realized in the next century. Fusion would be a relatively clean and almost limitless supply of energy, as can be seen from Table 7.1. To illustrate this, calculate how many years the present energy needs of the world could be supplied by one millionth of the oceans’ hydrogen fusion energy.
(b) How does this time compare with historically significant events, such as the duration of stable economic systems?
(a) One millionth of the oceans’ hydrogen fusion energy is enough to supply 25 million years of world’s energy.
(b) The time is much longer than human time scale.
Energy: The ability to perform work in physics. It can take many different forms, including potential, kinetic, thermal, electrical, chemical, nuclear, and others.
The fusion of all the hydrogen in Earth’s Ocean will produce of energy.
One millionth of this energy,
Annual world’s consumption of energy is,
Number of years of world’s energy supplied by one millionth of oceans’ hydrogen fusion energy is,
Putting all known values,
Therefore, One millionth of the oceans’ hydrogen fusion energy is enough to supply 25 million years of world’s energy.
The time 25 million years is a very long time, this time is much longer than a human can think of.
Thus, if we are able to use even one millionth of ocean’s hydrogen fusion energy, we will be able to supply enough energy for millions of years.
A skier with an initial speed of coasts up a high rise as shown in Figure 7.40. Find her final speed at the top, given that the coefficient of friction between her skis and the snow is . (Hint: Find the distance traveled up the incline assuming a straight-line path as shown in the figure.)
Figure 7.40 The skier’s initial kinetic energy is partially used in coasting to the top of a rise.
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