Convection currents in the Earth's mantle cause plate movement which can cause all except
2 answers:
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Answer:
14523.55J
Explanation:
The work done by the jogger against gravity is given by the following equation;
where m is the mass, g is acceleration due to gravity taken as and h is the height of the hill.
Since the length of the hill is 132m and it is inclined at 12 degrees to the horizontal, the height is thus given as follows;
Substituting this into equation (1) with all other necessary parameters, we obtain the following;
Answer:
3 km/h
Explanation:
Let's call the rowing speed in still water x, in km/h.
Rowing speed in upstream is: x - 2 km/h
Rowing speed in downstream is: x + 2 km/h
It took a crew 9 h 36 min ( = 9 3/5 = 48/5) to row 8 km upstream and back again. Therefore:
8/(x - 2) + 8/(x + 2) = 48/5 (notice that: time = distance/speed)
Multiplying by x² - 2², which is equivalent to (x-2)*(x+2)
8*(x+2) + 8*(x-2) = (48/5)*(x² - 4)
Dividing by 8
(x+2) + (x-2) = (6/5)*(x² - 4)
2*x = (6/5)*x² - 24/5
0 = (6/5)*x² - 2*x - 24/5
Using quadratic formula
A negative result has no sense, therefore the rowing speed in still water was 3 km/h