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Question: 
  1. Calculate the impulse experienced when a 55-kg person lands on firm ground after jumping from a height of 2.8 m.
  2. Estimate the average force exerted on the person’s feet by the ground if the landing is stiff-legged, and again
  3. with bent legs.

With stiff legs, assume the body moves 1.0 cm during impact, and when the legs are bent, about 50 cm. [Hint: The average net force on him, which is related to impulse, is the vector sum of gravity and the force exerted by the ground. See Fig. 7–34.] We will see in Chapter 9 that the force in (b) exceeds the ultimate strength of bone (Table 9–2).

Problem 24.

Source: Giancoli, Douglas C., Physics: Principles with Applications, 7th Edition, 2014.

Quick Answer: 
  1. $410\textrm{ kg m/s}$
  2. $1.5\times 10^5\textrm{ N}$
  3. $4000\textrm{ N}$

Giancoli 7th Edition, Chapter 7, Problem 24

(6:59)

Chapter 7, Problem 24 is solved.

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