A laser having with a spot 1.00 mm in diameter is shone perpendicularly on the center of a thin,perfectly reflecting circular (2.00 mm in diameter)aluminum plate mounted vertically on a flat piece of cork that floats on the surface of the water in a large beaker.The mass of this "sailboat" is 0.0550 g and it travels 3.00 mm in 50.0 s.Assuming that the laser power is constant in the region where the sailboat is located during the experiment,what is the power of the laser used in this demonstration? (Neglect air resistance and the viscosity of the water.)

Question

Quizplus · Accepted Answer

The power of the laser can be calculated using the principle of conservation of momentum and the fact that the force exerted by the laser on the sailboat is due to the change in momentum of the photons. The force causes the sailboat to accelerate, and from the distance traveled and the time taken, we can calculate the acceleration and hence the force. The power (P) of the laser is related to the force (F) and the speed of light (c) by the equation P = Fc. Given the mass of the sailboat, the distance traveled, and the time taken, we can calculate the acceleration, then the force, and finally the power of the laser. The correct calculation leads to the answer of 19.8 mW.

A Laser Having with a Spot 1