An athlete runs around a circular track.
Readings on the stop-watch used to time the athlete are shown for each lap.
How long did it take the athlete to run the third lap?
Correct Answer: \( \boxed{\mathrm{A}} \)
The time for the third lap is found by subtracting the total time after two laps from the total time after three laps.
After two laps: \(T_{2}=2\times 60+59=179\,\mathrm{s}\)
After three laps: \(T_{3}=4\times 60+18=258\,\mathrm{s}\)
Time for the third lap:
\( \Delta t=T_{3}-T_{2}=258-179=79\,\mathrm{s} \)
Converting \(79\,\mathrm{s}\) into minutes and seconds:
\(79\,\mathrm{s}=1\,\mathrm{min}\ 19\,\mathrm{s}\)
Therefore, the athlete took \(1\,\mathrm{min}\ 19\,\mathrm{s}\) to complete the third lap.
Hence, the correct answer is (A).
A girl uses a ruler to measure the length of a metal rod. The end of the ruler is damaged, so she places one end of the rod at the \(1\,\mathrm{cm}\) mark, as shown.
How long is the metal rod?
Correct Answer: \( \boxed{\mathrm{B}} \)
Since the end of the ruler is damaged, the measurement must be found by subtracting the initial reading from the final reading.
Initial reading \(= 1.0\,\mathrm{cm}\)
Final reading \(= 5.6\,\mathrm{cm}\)
Length of rod:
\( \mathrm{Length} = 5.6 – 1.0 = 4.6\,\mathrm{cm} \)
Converting to millimetres:
\( 4.6\,\mathrm{cm} \times 10 = 46\,\mathrm{mm} \)
Therefore, the length of the metal rod is \(46\,\mathrm{mm}\).
Hence, the correct answer is (B).
Which measuring instrument is used to determine the volume of water in a cup?
Correct Answer: \( \boxed{\mathrm{B}} \)
A measuring cylinder is the standard laboratory instrument used to measure the volume of liquids directly.
A clock is used to measure time, a ruler is used to measure length, and a thermometer is used to measure temperature.
Since water is a liquid, it takes the shape of its container and its volume is determined by reading the graduated scale on a measuring cylinder.
Therefore, the correct answer is (B) measuring cylinder.
