I gave the following problem as an extra credit exercise on a test for my
Honors physics.
What would you say the solution was? I believe it is from Tipler Physics. I
don't have an answer key for the book so I am not sure. A couple of kids got
into a pretty good debate (until the soccer coach arrived and chewed them
out) over what the solution is or was.
Jim
jharris@monad.net or jharris@newpisgah.keene.edu
Teacher: Monadnock Regional High School
Adjunct Faculty: Keene State College, Chemistry Department
EXTRA CREDIT Jack/Jill is strolling along the bank of a river 1 km wide
when the most beautiful/handsome girl/boy he/she has ever seen materializes
on the shore directly opposite him/her (perhaps she/he was beamed down?).
Fearing that she/he will disappear before he/she has a chance to establish
face-to-face communication, he/she quickly devises a plan to reach the
opposite shore in the shortest possible time. In the wildest of
coincidences, there is a rowboat beached on the shore right in front of
him/her. Jack/Jill is ecstatic, because it so happens that he/she's an
expert oarsperson. (He/she rows on the crew for an ivy league school.)
He/she knows that he/she can row at a speed of 6 km/h in still water, and
he/she estimates--as he/she sprints for the boat at 10 km/h--that the river
current has a speed of 4 km/h. Now, besides being an athlete and an
excellent judge of river velocities, Jack/Jill is also an accomplished
physics student. During his/her sprint to the boat, he/she computes the path
he/she must take from his/her side of the river to reach the girl/boy on the
opposite side in the shortest possible time. In general, his/her path
includes a diagonal trip across the river followed by a sprint along the
opposite shore to reach his/her goal. (Note that Jack/Jill has a standard
sprinting speed of 10 km/h.) Assuming that Jack/Jill did the physics
correctly, in what direction did he/she head the boat and how long did it
take him/her to establish first contact?