Calculate the period of wave whose frequency is 50Hz

Electromagnetic induction. a coil of wire contains n turns and has an electrical resistance r. the radius of each turn is a. initially, inside the coil there exists a uniform magnetic field of magnitude b0 parallel to the axis of the coil. the magnetic field is then reduced slowly. the current induced in the coil is i. how long does it take for the magnitude of the uniform field to drop to zero?

The friction of the water on a boat produces an acceleration of -10. m/s2. if the boat is traveling at 30. m/s and the motor is shut off, how long it take the boat to slow down to 5.0 m/s?

An astronaut on the moon throws a baseball upward. the astronaut is 6 ft, 6 in. tall, and the initial velocity of the ball is 3030 ft per sec. the height s of the ball in feet is given by the equation s equals negative 2.7 t squared plus 30 t plus 6.5s=−2.7t2+30t+6.5, where t is the number of seconds after the ball was thrown. complete parts a and b.