Physics
(a) A pulley cannot have 100% efficiency. Explain why?
(b) How is the unit 'horsepower' related to the SI unit of power?
(c) Write the two uses of radioactivity.
Answer
(a) As some effort is wasted in overcoming the friction between the strings and the grooves of the pulley as a result the efficiency of a movable pulley is always less than 100%.
(b) 1 horse power = 746 watt.
(c) Uses of radioactivity :
- Many diseases such as leukemia, cancer, etc., are cured by radiation therapy.
- Radioisotopes are used to trace and study the uptake of nutrients by plants. For example, the use of radioactive phosphorous 32P in fertilizers has revealed how phosphorous is absorbed by plants.
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