Which of the following is an accurate statement? a. ac generators produce current that is pulsating, but always remains positive. b. step-up voltage transformers have a lower number of turns in the primary than in the secondary winding. c. dc generators produce current with a voltage that changes from positive to negative. d. step-down voltage transformers have a different number of turns in the primary than in the secondary winding, so they change the incoming voltage to a higher voltage.

Aball bearing at 220.0 °c is dropped into a cup containing 250.0 g of water at 20.0 °c. the water and ball bearing come to a temperature of 30.0 °c. what is the heat capacity of the ball bearing in j/°c? (hint: how are the algebraic signs of q related for the ball bearing and the water? )

Ablock of mass m = 2.5 kg is attached to a spring with spring constant k = 710 n/m. it is initially at rest on an inclined plane that is at an angle of θ = 23° with respect to the horizontal, and the coefficient of kinetic friction between the block and the plane is μk = 0.19. in the initial position, where the spring is compressed by a distance of d = 0.16 m, the mass is at its lowest position and the spring is compressed the maximum amount. take the initial gravitational energy of the block as zero. a) what is the block's initial mechanical energy? b) if the spring pushes the block up the incline, what distance, l, in meters will the block travel before coming to rest? the spring remains attached to both the block and the fixed wall throughout its motion.

Order the sequence of ideas that lead to marie curies discovery of radioactive elements number the events in chronological order starting with the oldest