Cho mạch điện như hình vẽ tìm các dòng I1, I2 , I3 và I4 biết E1 = 120V, E2 = 60V, J = 10A, R1= R2= 20Ω. R3= R4= (10 + K) Ω
(k=5)

An athlete swings a ball, connected to the end of a chain, in a horizontal circle. the athlete is able to rotate the ball at the rate of 8.13 rev/s when the length of the chain is 0.600 m. when he increases the length to 0.900 m, he is able to rotate the ball only 6.04 rev/s. (a) which rate of rotation gives the greater speed for the ball? 6.04 rev/s 8.13 rev/s (b) what is the centripetal acceleration of the ball at 8.13 rev/s? m/s2 (c) what is the centripetal acceleration at 6.04 rev/s? m/s2