Which of the following objects is an example of a luminous source? a. sun

b. moon

c. desk

d. all of these

e. none of these

If the spring constant k of a pogo stick is 3500 n m and the weight of the person on the pogo stick is 700 n, how much is the spring in the botom of the pogo stick compressed?

What is the efficiency of an engine that does 80 j of work and exhausts 320 j of heat while taking in 400 j of heat ? a. 10% b. 20% c. 80% d. 25%

Aswimming pool whose volume is 10 comma 000 gal contains water that is 0.01% chlorine. starting at tequals0, city water containing 0.003% chlorine is pumped into the pool at a rate of 5 gal/min. the pool water flows out at the same rate. what is the percentage of chlorine in the pool after 1 hour? when will the pool water be 0.006% chlorine?