螺丝和螺母很紧，最有可能使之变松的方法是整体加热还是制冷（见题）

Question

A nut is verytight on a screw ，which of the following is most likely tofree it?
A. cooling it
B. heating it
C. either
D. neither
再来一问. When a caraccelerates forward, it tends to rotate about its center of mass. The car willnose upward
A. when thedriving force is imposed by the rear wheels (for front-wheel drive the carwould nose downward)
B. Whether drivingforce is imposed by the rear or the front wheel

Answer 1

应该选D吧，一般螺丝和螺母都用一样的材料，受热膨胀系数也是一样，加热会同时向外膨胀，不会变松追问

再来一问：When a caraccelerates forward, it tends to rotate about its center of mass. The car willnose upward

Answer 2

热胀冷缩。