撞擊力問題(phy)

A simple approach is to use: impulse = change of momentum
i.e. impact force x duration of impact = mass x velocity

Generally, it is difficult to estimate the impact time, as it depends very much on the nature of the falling object and the surface onto which the object makes impact with. But in normal ciecumstances, it is around 0.1 to 0.5 seconds.

With the data given in your question, we could estimate the impact time in this particular example,

impact time = mass x velocity/imapct force
with mass = 45 kg
velocity = 143 km/h = 40 m/s
impact force = 457 kgf = 4570 N (take g = 10 m/s2)
hence, impact time = 45 x 40/4570 s = 0.4 s