Một chất điểm chuyển động tròn đều trên quỹ đạo có bán kính r = 40cm với chu kì T= 2s. Tính tốc độ góc, tốc độ dài và gia tốc hướng tâm của chất điểm.

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?

Select all the correct answers. which three statements about electromagnetic radiation are true?

How is the ideal mechanical advantage of a wheel and axle calculated?