A river has a steady speed of 0.30 m/s. A student swims downstream a distance of 1.2 km and returns to the starting point. If the student swims with respect to the water at a constant speed and the downstream portion of the swim requires 20 minutes, how much time is required for the entire swim?
A. 50 minutes
B. 80 minutes
C. 90 minutes
D. 70 minutes
E. 60 minutes
Answer: D
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How should we expect the Milky Way's interstellar medium to be different in 50 billion years than it is today?
A) The total amount of gas will be much less than it is today. B) The total amount of gas will be about the same, but the percentage of elements heavier than hydrogen and helium will have risen from the current 2% to more than 50%. C) The total amount of gas will be much greater because many stars will undergo supernovae between now and then. D) Thanks to the recycling of the star-gas-star cycle, the interstellar medium should look about the same in 50 billion years as it does today.
The brakes in a car work because of
a. Archimedes' principle. b. Pascal's principle. c. Bernoulli's principle. d. Torricelli's principle. e. none of these principles.
When unequal resistors are connected in parallel in a circuit,
A) the same current always runs through each resistor. B) the potential drop is always the same across each resistor. C) the largest resistance has the largest current through it. D) the power generated in each resistor is the same.
Grandfather clocks are designed in a way that the weight at the bottom of the pendulum can be moved up or down by turning a small screw. Suppose you have a grandfather clock at home that runs fast
Should you turn the adjusting screw so as to raise the weight or lower the weight? A) Raise it. B) Lower it. C) It doesn't matter if you raise or lower the weight, as long as you displace it by the right amount. D) It doesn't matter if you raise or lower the weight, as long as you displace it with the correct initial velocity. E) Raising or lowering the weight doesn't help, the screw is there so that you can add or take away weight.