For a photoelectric tube, calculate the voltage which will be just sufficient to stop electrons emitted by the sodium photo-plate reaching the collector plate when light of frequency 6 x 1014Hz is incident on a sodium plate. Addition information: 1 e = 1.6 x 10-19C Plank's Constant, h = 6.64 x 10-34 Work function, Wo, of sodium = 2.2 x 10-19J

Electric field of the earth. the earth has a net electric charge that causes a field at points near its surface equal to 150 n> c and directed in toward the center of the earth. (a) what magnitude and sign of charge would a 60-kg human have to acquire to overcome his or her weight by the force exerted by the earth’s electric field? (b) what would be the force of repulsion between two people each with the charge calculated in part (a) and separated by a distance of 100 m? is use of the earth’s electric field a feasible means of flight? why or why not?

How do the kidneys affect homeostasis

Abird flies directly overhead from where you stand at an altitude of 300.0 m and at a speed horizontal to the ground of 20.0 m/s. the bird has a mass of 2.0 kg. the radius vector to the bird makes an angle \thetaθ with respect to the ground. the radius vector to the bird and its momentum vector lie in the xyxy-plane. what is the bird’s angular momentum about the point where you are standing?