【单选题】A 50-kg person stands on a 25-kg platform. He pulls on the rope that is attached to the platform via the frictionless pulley system shown here. If he pulls the platform up at a steady rate, with how m...
【简答题】How a person handles space in dating others is an obvious and very sensitive indicator of how he or she feels about the other person. On a first date,if a woman sits or stands so sclose to a man that ...
【判断题】A person stands on a bathroom scale in an elevator. When the scale reads only 75% of the person’s regular weight, he claims that the elevator must be moving downward. Is he right?
【单选题】A person swings on a swing. When the person sits still, the swing oscillates back and forth at its natural frequency. If, instead, the person stands on the swing, the natural frequency of the swing is