Problem 4.20 Part A Mary needs to row her boat across a 140 m -wide river that i
ID: 1658598 • Letter: P
Question
Problem 4.20 Part A Mary needs to row her boat across a 140 m -wide river that is flowing to the east at a speed of 1.5 m/s. Mary can row with a speed of 3.5 m/s If Mary points her boat due north, how far from her intended landing spot will she be when she reaches the opposite shore? Express your answer using two significant figures 0 SE meters east (downstream) from where she intended Submit My Answers Give Up Part B What is her speed with respect to the shore? Express your answer to two significant figures and include the appropriate units u= Value Units Submit My Answers Give UpExplanation / Answer
width of river , d = 140 m
speed of river , u = 1.5 m/s
speed of mary , v = 3.5 m/s
part A)
if she is rowing in north direction
time taken = d/v
time taken = 140/3.50
time taken = 40 s
drift of boat from the spot = time taken * u
drift of boat from the spot = 40 * 1.5
drift of boat from the spot = 60 m
part B)
for the speed wrt shore
speed wrt shore = sqrt(v^2 + u^2)
speed wrt shore = sqrt(1.5^2 + 3.5^2)
speed wrt shore = 3.81 m/s
the speed with respect to the shore is 3.81 m/s