Historical theoretical question: “To prevent mosquitoes breeding in your aquarium, you can put ….” The choices below reproduce the 2009 paper, not safe aquarium-care instructions. Do not try these additions in an aquarium containing living animals. Discuss the intended mechanism and the safety problem.
A. A teaspoon of salt per liter of water
B. A drop of concentrated detergent per liter of water
Mr. Sony is a scientist. He noticed bacteria growing on a plate of agar. Bacteria did not grow near a mold that appeared on the same plate. He wrote in his laboratory report: “The mold may produce a substance that kills bacteria.” This statement is best described as which of the following?
Mr. Jury has mass 60 kg and has gained an excess of 2000 calories from food, where this problem explicitly defines 1 calorie = 4.2 joules. For every 1 meter of vertical stair height he climbs, the energy used in joules equals 10 times his mass in kilograms. Calculate the height required to use the stated energy in this simplified model.
At night, a stadium is illuminated with red light. Team P wears white shirts and black shorts. Team Q wears red shirts and green shorts. Both teams seem to have the same uniform colors. Explain why.
The diagram shows a mercury-in-glass laboratory thermometer. The distance between the 0°C and 70°C marks is 35 cm. Calculate the temperature when the mercury reaches 42 cm measured from the 0°C mark.
Two balls of unequal masses are connected by a light rigid rod. A force through their center of mass (CM) moves the system in the force direction without rotating it.
a) What happens when the force is applied between the less massive ball and CM?
b) What happens when it is applied between the more massive ball and CM?
Temperature is an abiotic factor affecting metabolism, including respiration. In the source’s hypothetical aquarium scenario, how would cooling the water with ice affect fish respiration? Discuss theoretically only; do not carry out abrupt cooling on live fish.
A city is supplied by a reservoir on high ground. Water flows through pipes when a tap is opened. Why does water usually flow out more rapidly from a first-floor tap than from taps on upper floors of an apartment building?
Why should the amalgam used in a dental filling have thermal expansion similar to that of the tooth? What could happen if their expansions were mismatched?
