Mr. Smith was very sad to find the TV set he had had ______ went wrong again. A. to be repaired B. it repaired C. it D. repaired 答案:D如图所示,小明同学骑着一辆自行车在平直公路上匀速运动300m,所用时间为60s.假设自行车在行驶过程中受到的阻力为100N.求:(1)自行车行驶的速度.(2)在这段过程中,小明同学骑车的功率.(3)若小明和自行车总重600N,车胎与地面总的接触面积为40cm2,则小明骑车时,自行车对地面的压强为多大?