Question

EXERCISE HINTS: GETTING STARTED I'M STUCKI A laser has a power of 20.0 W and a beam radius of 0.549 mm. (a) Find the intensity of the laser. 2.11E7 I W/m2 (b) Suppose you were floating in space and pointed the laser beam away from you. What would your acceleration be? Assume your total mass, including equipment, is 73.3 kg and that the force is directed through your center of mass. Hint: The change in momentum is the same as in the nonreflective case. 1.3111E-3 x We know that the acceleration of an object is given by Newton's second law. How do we determine the net force acting on the accelerating object in this case? m/s? (c) Calculate your acceleration if it were due to the gravity of a space station with mass 1.20 x 109 kg and center of mass 115.0 m away. m/s2 (d) Calculate the peak electric and magnetic fields of the laser. Emax = N/C Bmax = If you were planning to use your laser welding torch as a thruster to get you back to the station, don't bother because the force of gravity is stronger. Better yet, get somebody to toss you a line. Submit Answer Practice Another Version

Answer 1

a)The intensity of laser is, 20 (0.549x103) = 2.11x10 W/m b)The momentum of photon is, hv Forn -photons The force due to laser is, F-nhv But laser power is, Penhy Therefore, the force is, 20 3x108 = 6,67x10-3 The acceleration is, a=- hel 6.67x10-8 733 = 9.09959x10-10 =9.1x10-10m/s2 C)The gravitational force is equal to the normal force F-GMM = ma The acceleration is, a= GM (6.67x10-1)(1.2x100) 1152 = 6.05x10 m/s2

d)The intensity of electromagnetic wave is, 1CH Em = 2IC JI = 1/2(2.11x107)(3x10°)(41x 10-") = 1.26x10 N/C 1.26x10 3x108 = 4.2x10-1