Dr. trout has noticed that salmon in his fish hatchery seem to enjoy listening to the radio in his lab. the fish in the tank closest to the radio seem to grow larger. dr. trout decides that the more music he plays, the larger the fish must grow. to test his idea, he sets up 5 large ponds with 100 salmon in each pond. he places a loudspeaker at the middle of each pond and plays various amounts of music in each pond. he plays the same band, feeds the fish the same diet, and keeps water conditions in all tanks exactly the same. after 10 weeks, he ends the trial and takes the average mass of the fish in each pond, and presents his data in the table. the independent variable in dr. trout's experiment is a) type of fish. b) the fish diet. c) type of music played. d) hours of music played.

C) type of music played.  

Explanation:

The independent variable in an experiment can be changed and manipulated so as to know it's effect over the dependent variable, which is the outcome of the experiment.

The type of music played is the independent variable this is because of the fact that the type of music played and the amount of music played has been changed so as to know it's effect on the growth of the fish.  

air exerts forces on falling objects near earth’s surface.

explanation:

the term 'free falls' refer to object that are falling towards the earth, in a situation in which gravity is the only force acting on the object.

for an object in free fall, the acceleration is constant (g, the gravitational acceleration), and so the velocity of the object constantly increases.

for objects near earth's surface, there is always another force acting on the object: the resistance due to the air. this force is opposed to the direction of fall of the object, and it is proportional to the velocity of the object, so as the object falls down, this force increases up to a point when it balances the force of gravity, and the object continues its motion at constant velocity (called terminal velocity). since in this case gravity is not the only force acting on the object, we are not in a situation of free fall.

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