Final answer:
Catching a ball by 'giving in' and hitting water with fingers first both extend the impact duration, reducing the force experienced. This demonstrates principles of impulse in physics. Belly flops are advised against due to the high force of impact caused by abrupt stopping against a large area.
Step-by-step explanation:
The actions described involve fundamental concepts of impulse and the forces exerted during different types of impact. When catching a ball while 'giving in' with it, you are effectively increasing the time over which the ball comes to a stop, thereby reducing the force of the impact. This is because impulse is the product of force and time, and for a given change in momentum, increasing the time will decrease the force. In contrast, keeping your hands still provides a much shorter impact time, leading to a greater force over that shorter period.
Similarly, when you hit water with your full palm, the large area of impact and the abrupt stop result in a high force, simulating the uncomfortable experience of a belly flop. However, when you hit the water with your fingers first, the force is distributed over a longer period and the smaller area of contact (the fingers) enter the water one by one, which minimizes the force felt. Therefore, people are generally advised to avoid belly flops and instead dive with their hands first to reduce the impact force.