物理
1. a uniform horizontal beam, 14m long, is support at point A and B, 2m and 6m respectively, from one end. if the supporting force at A is 300N. calculate
a. the wight of the beam
B. the supporting force at B
2. A 12-V 24Wlamp is connected to a 30-V . the value of the resistor Ris selected so that the lamp is operated at its rated voltage and power. find
a. the current through the lamp
b. the resistance of the lamp
c. the resistance of R