【单选题】A 2.0-kg ball is moving with a constant speed of 5.0 m/s in a horizontal circle whose diameter is 1.0 m. What is the magnitude of the net force on the ball? A) 0 N B) 20 N C) 40 N D) 50 N E) 100 N
【单选题】There is a toroidal magnetic core with an average length L= 40 cm=0.4m, a cross-sectional area S=10 cm.^2, a number of turns N=300, a current I= 1.2A, and a magnetic field strength of H=___A/m. HL=NI...