✔ 最佳答案
Q.1. The answer is (2) and (3).
Remind that impulse = change of momentum
Ft = m(v - u)
For the same change of momentum, the longer the impact time, the smaller the impact force exert on the person and hence the danger is reduced.
(1) For a rigid body, the impact time will be very small, this will be very dangerous for the passenger since the impact force will be very large.
(2) The seat belts can lengthen the impact time and hence greatly reduce the impact force acting on the man.
(3). The air bags have cushion effects to increase the time of impact.
Q.2. For E.M. waves, the shorter the wavelength (that is the higher the frequency), the higher the penetrating power is since it is directly proportional to frequency of the wave.
So, ultraviolet radiation has a higher penetrating power than visible light since it has a shorter wavelength.
