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I'm having some troubles with some more rates questions and was wondering if someone could help me out.

A construction worker pulls a 5m plank up the side of a building under construction by means of a rope tied to the end of a plank. The opposite end of the plank is being dragged along the ground. If the worker is pulling at a rate of 15 cm/s, how fast is the end of the plank sliding along the ground when it is 2m from the wall of the building?

A fish is being reeled in at a rate of 30cm/s from a bridge 4m above water. At what rate is the angle (in rad/s) between the line and the water chaning when there is 8m of line out?

The relation between distance s and velocity v is given by v = 150s/(3+s). Find acceleration in terms of s.

I had no clue how to do the first two, but I thought I could do the second so I found the first and second derivative of the equation thinking that it would give me the answer but it did not, so I guess I am more lost than I though. Any help would be greatly appreciated.

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