An unusual lightning strike has a vertical portion with a current of −400 a downwards. the earth's magnetic field at that location is parallel to the ground and has a magnitude of 30 μt. calculate, in n, the force exerted by the earth's magnetic field on the 25-m-long current.

The image shows a pendulum in simple harmonic motion the pendulum starts at a and swing to e

Amoving electron has kinetic energy k1. after a net amount of work w has been done on it, the electron is moving one-quarter as fast in the opposite direction. (a) find w in terms of k1. (b) does your answer depend on the final direction of the electron's motion?

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?