To solve the shock problem, you need to use the momentum theorem. F=ma F=mv/t

∴ Ft = mv

That is: impact force × impact time (impulse) = mass of the impact object × speed (momentum) at the moment of impact

At the moment when the impact occurs, the right side of the formula is a fixed value, so the magnitude of the impact force is inversely proportional to the length of the impact time. (Therefore, air-cushion objects are generally used to catch the falling person to prolong the release time between the person and the air-cushion, that is, the impact time, and reduce the impact force)

In the problem of lz, suppose the child weighs 9kg, falls 15m, and the acceleration of gravity g=10. Then the moment the child is picked up, the child's momentum is:

mv=mgt=mg(2S/g)^0.5=9×10×(2×15÷10)^0.5=90*root number 3 (kg m/s)

According to the momentum theorem, the product of the impact force and the impact time of the courier picking up the child is 90*square 3 (N s)

If the courier directly picks up the child with both arms, the arm does not perform a downward buffering unloading action immediately after receiving the child. Assuming that the child is stationary after the contact time of 0.1 seconds, the impact force at this time is:

F=mv/t=(90*square 3)÷0.1=900*square 3 N

If the courier buffers his arm downwards at the moment of receiving the child, and stops the child after one second, the impact force is:

F=mv/t=(90*square 3)÷1=90*square 3 N