Concept explainers
(a)
The final velocity when a person jumps from 2.8 m high roof.
(a)
Answer to Problem 18P
Solution:
Final velocity of person is
Explanation of Solution
Given:
Initial velocity when a person jumps off the roof,
Acceleration during free fall,
Height through which person falls,
(b)
To find: Final velocity as person lands on the ground,
Formula:
Third equation of motion:
Where,
Calculation:
Substitute the vales and solve for final velocity.
(b)
Explanation of Solution
Conclusion: Free fall concept helps to determine the final velocity of a person as he lands on the ground is
c)
The average force exerted on person’s torso by his legs during deceleration.
c)
Answer to Problem 18P
Solution:The average force exerted on person’s torso by his legs during deceleration is
Explanation of Solution
Given:
Initial velocity when torso deceleration starts after landing on the ground,
Final velocity when all kinds of motions ceased,
Mass of person’s leg,
(d)
To find: (I)Deceleration of person’s legs,
(II)Force on torso during deceleration,
(d)
Explanation of Solution
Formula Used:
Third equation of motion:
Where,
From Newton’s second law of motion:
Where, m is mass and a is acceleration.
Calculation:
(I)Substitute the values in the third equation of motion and solve for acceleration (a)
Thus, deceleration =
(II) Using Newton’s second law, calculate the average force exerted by legs on torso during deceleration.
Conclusion: Using Newton’s second law, the average force exerted by legs on torso during deceleration is
Chapter 4 Solutions
Physics: Principles with Applications
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