Final answer:
The Physics concept of change in momentum can explain why bending your knees when jumping from a height reduces impact force. Bending the knees increases the time over which momentum change occurs, thus reducing the force exerted on the body due to Newton's second law.
Step-by-step explanation:
The subject matter related to this question is Physics as the student is asking about a kinematic event related to jumping from some height. In Physics, when one jumps from a certain height and lands by bending their knees, the time over which the change in momentum (∆p) is taking place is increased. This is represented by the relation F ∆t = m∆v. Here, F is the force, t is time, m is mass, and v is velocity.
When you bend your knees, the force exerted over your body due to the stop in momentum is spread out over a longer duration, thus reducing the impact force. This is why it's less jarring and generally safer to bend your knees as you land. The change in momentum is absorbed over a larger time, resulting in a smaller force exerted on your body due to Newton's second law of motion. This reduces the potential harm caused by the sudden deceleration when landing.
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