For the same setup of the "Faraday Law" experiment, if the frequency of the magnetic field is changed from 40Hz to 120Hz, how will the emf voltage change? a) will increase three times b) will not change c) will decrease three times d) will change the sign e) will decrease by 80 V f) will increase by 80 V

As you are trying to move a heavy box of mass m, you realize that it is too heavy for you to lift by yourself. there is no one around to , so you attach an ideal pulley to the box and a massless rope to the ceiling, which you wrap around the pulley. you pull up on the rope to lift the box. use g for the magnitude of the acceleration due to gravity and neglect friction forces. once you have pulled hard enough to start the box moving upward, what is the magnitude f of the upward force you must apply to the rope to start raising the box with constant velocity? express the magnitude of the force in terms of m, the mass of the box.