
Concept explainers
(a)
The internal work-done by the athlete.
(a)

Answer to Problem 68P
400 Joules
Explanation of Solution
Given:
The center of mass of athlete moves 0.500 meters.
The muscular energy that needs to be spent on the athlete to lift his body is 800 N.
Formula Used:
The work-done by the internal energy is
Calculation:
800 N is basically the force that is needed to overcome by the gravity to jump upward.
Conclusion:
The work-done by the internal energy of jumper is 400 Joules.
(b)
The speed of the athlete.
(b)

Answer to Problem 68P
Explanation of Solution
Given:
The center of mass of athlete moves 0.500 meters.
The muscular energy that needs to be spent on the athlete to lift his body is 800 N.
Formula Used:
The potential energy is equal to the kinetic energy of the athlete
Calculation:
Considering
Conclusion:
The speed is
(c)
The time of jump for given height.
(c)

Answer to Problem 68P
The time required to reach 0.400 m height by the jumper will be 0.5145 sec.
Explanation of Solution
Given:
Initial speed,
Final speed,
Formula Used:
Calculation:
Negative sign shows the deceleration.
Now, the acceleration of the jumper is
Solving the equation, t will be -0.1174 seconds.or 0.5145 seconds. Negative time does not make any sense. Hence, the t will be 0.5145 seconds.
Conclusion:
The time required to reach 0.400 m height by the jumper will be 0.5145 s.
(d)
The average mechanical power.
(d)

Answer to Problem 68P
Explanation of Solution
Given:
Initial speed,
Final speed,
Formula Used:
Calculation:
Negative sign shows the deceleration.
Now, the acceleration of the jumper is
As,
Conclusion:
The average power is 1265.822 Watts.
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Chapter 7 Solutions
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