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A runner is jogging in a straight line at a steady v, 3 km/hr. When the runner is L= 5.9 km
from the finish line, a bird begins flying straight from the runner to the finish line at
v= 12 km/hr (4 times as fast as the runner). When the bird reaches the finish line,
it turns around and flies directly back to the runner.
What cumulative distance does the bird travel? Even though the bird is a dodo,
as- sume that it occupies only one point in space (a "zero" length bird),
travels in a straight line, and that it can turn without loss of speed.
Answer in units of km.
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The bird is flying the same time as a runner is running, but has the speed,
which is 4 times as great as the runner has.
Therefore, while the runner is running, the bird will cover the distance, which is
4 times as long, as the distance covered by the runner, i.e. 4 x 5.9 km = 23.6 kilometers.
ANSWER. The cumulative distance the bird will travel is 23.6 kilometers.
Solved.
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It is well known entertainment problem.