A sinusoidal electromagnetic wave has an average intensity of I1 =100 W/m2. By what factor would the electric-field amplitude of the wave have to be increased in order for the wave to have an average intensity of I2 = 8100 W/m2 ?

Diego is trying to lift a piano to the second floor of his house. diego uses a pulley system and gives a big lift to the piano. the piano moves upward, then stops, and then it starts to fall to the ground. which list best describes the forces on the piano in the proper order? positive force → balanced force → negative force negative force → balanced force → positive force positive force → unbalanced force → negative force negative force → unbalanced force → positive force