A boat is moving in a uniform straight motion at a certain speed v. If a braking force of 210 N is applied for a distance of 5 m, how much power is developed by the braking force?
A) 210 W
B) 105 W
C) 1050 W
D) 420 W
E) 8,4 W
IMAT 2024 · Question 55
Q55 - Work, energy and power
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The correct answer is A) 210 W.
The official key says 210 W, but strictly this question can't be answered from the data.
What you can calculate is the work: W = F × d = 210 × 5 = 1050 J. Power needs either the time or the speed (P = F × v), and the question gives neither. 210 W only works if you assume v = 1 m/s, which the question never says.
In the exam you'd pick 210 W as the intended answer. 1050 is the right number for the work, but it's in joules, not watts.
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