Laser Beam Propulsion 017 10.0 points An astronaut in a spacecraft moving with c
ID: 2036420 • Letter: L
Question
Laser Beam Propulsion 017 10.0 points An astronaut in a spacecraft moving with constant velocity wishes to increase the speed of the craft by using a laser beam attached to the spaceship. The laser beam emits 95 J of electromagnetic energy per pulse at the rate of 0.08 pulse/s. The mass of the spaceship plus its contents is 6092 kg The speed of light is 3 x 106 m/s. For how long must the beam be on in order to increase the speed of the vehicle by 0.5 m/s in the direction of its initial motion? 1. 48158600000.0 2. 113672000000.0 3. 70020500000.0 4. 34810900000.0 5. 127824000000.0 6. 65891500000.0 7. 120237000000.0 8. 51287700000.0Explanation / Answer
We know that Change in momentum is given by:
F = dP/dt
F = m*dV/dt
Also Force is given by
F = P/V
V = speed of light = c
Total power carried by laser will be
Power = P = energy/time
P = E*f
f = frequency = 0.08 pulse/sec
F = E*f/(c)
E*f/c = m*dV/dt
dt = m*dV*c/(E*f)
Using given values:
dt = 6092*0.5*3*10^8/(95*0.08)
dt = 1.202*10^11 sec
Correct option is 7
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