Physics Uniform Motion

Question

A motorboat can maintain a constant speed of 16 miles per hour relative to the water. The boat makes a trip upstream to a certain point in 20 minutes; the return trip takes 15 minutes. What is the speed of the current?

Answer 1

The distance d the motorboat traveled to reach a certain point was

 

d = 20 minutes * (16mph/60 minutes per hour)

   = 5 1/3 mi

 

Since the return trip took 15 minutes, the motorboat was going at a speed of 

(5 1/3 mi ÷ 15 minutes) * 60 minutes per hour = 21 1/3 mph

 

If the motorboat can maintain a speed of 16mph, then the speed of the current would be 21 1/3 - 16 = 5 1/3 mph.