A crane lifts a steel submarine of density 7800 kg/m3 and mass 20,000 kg. What is the tension in the lifting cable (a) when the submarine is submerged in water of density 1000 kg/m3, and (b) when it is entirely out of the water? A) (a) 2.0 x 10^5 N (b) 2.6 x 10^3 N
B) (a) 2.0 x 10^5 N (b) 1.7 x 10^5 N
C) (a) 2.6 x 10^3 N (b) 2.0 x 10^5 N
D) (a) 1.7 x 10^5 N (b) 2.0 x 10^5 N

Ithink the answer would be 1,350!

The best answer would be the first option a).

Part of the text of the exercise is missing.complete text: "a semiconductor laser in a cd player has an output wavelength of 780nm and a power level of 0.10mw. how many photons strike the cd surface during the player of a cd 69 minutes in length? ? "solutionthe power is the energy per unit of time; the laser power is  , and it is applied for a time t of  . from the previous equation we can find the total energy delivered by the laser during this time: then we can find the frequency of the photons of the laser light. in fact, we know the relatioship between c (speed of light), f (frequency) and  (wavelength): using  and  , we getfrom this, we can find the energy carried by one single photon of this frequency: and finally, we can find the number of photons dividing the total energy delivered by the laser by the energy carried by one single photon: