Answer:
The horizontal forces are equal in size and opposite in direction. They are balanced, so the horizontal resultant force is zero. This means that there is no horizontal acceleration just a horizontal constant speed. If a submarine is not moving horizontally, then there are no horizontal forces.
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Answer:
Food Chain. A food chain shows you how one organism eats another and transfers its energy. For example, a zebra eats grass, and the zebra is eaten by the lion.
<h3><u>Answer;</u></h3>
= 4,320,000 joules
<h3><u>Explanation;</u></h3>
Power is the ratio of Work per unit time. When work is done in a given span of time, the ratio of work performed with respect to time is called Power.
Therefore;
Power = Work done/time
Power = 1200 Watts and t = 1 hour or 3600 seconds
Thus;
Work done = Power × time
= 1200 × 3600
= 4,320,000 joules or 4320 kJ
m = mass of the boulder = 100 kg
h = height of the cliff from which boulder falls = 50 m
g = acceleration due to gravity = 9.8 
v = speed of boulder just before it hits the ground = ?
Using conservation of energy
Kinetic energy of boulder just before hitting the ground = Potential energy of boulder at the top of cliff
(0.5) m v² = mgh
dividing both side by "m" , "m" cancel out and we get
(0.5) v² = gh
inserting the values
(0.5) v² = (9.8) (50)
v = 31 
Hence correct choice is A. 31 m/s
