Concept explainers
A football player pushes a 670-N blocking sled. The coefficient of static friction between sled and grass is 0.73, and the coefficient of kinetic friction between sled and grass is 0.68.
a. How much force must the player exert to start the sled in motion?
b. How much force is required to keep the sled in motion?
c. Answer the same two questions with a 100-kg coach standing on the back of the sled.
a)
To determine: The force required to cause the sled in motion.
Answer to Problem 5IP
The force required to cause the sled in motion is greater than
Explanation of Solution
Calculation:
Write an expression to find the force required to cause the sled in motion.
Here,
Substitute 0.73 for
Therefore, the force required to cause the sled in motion is greater than
Therefore, the force required to cause the sled in motion is greater than
b)
To determine: The force required to keep the sled in motion.
Answer to Problem 5IP
The force required to keep the sled in motion is greater than
Explanation of Solution
Calculation:
Write an expression to find the force required to keep the sled in motion.
Here,
Substitute 0.68 for
Therefore, the force required to keep the sled in motion is greater than
Therefore, the force required to keep the sled in motion is greater than
c)
To determine: The force required to cause the sled and coach in motion.
Answer to Problem 5IP
The force required to cause the sled and coach in motion is greater than
Explanation of Solution
Calculation:
Calculate the total reaction force.
Here,
Substitute
Therefore the total reaction force is
Write an expression to find the force required to cause the sled and coach in motion.
Here,
Substitute 0.73 for
Therefore, the force required to cause the sled and coach in motion is greater than
Therefore, the force required to cause the sled and coach in motion is greater than
To determine: The force required to keep the sled and coach in motion.
Answer to Problem 5IP
The force required to keep the sled and coach in motion is greater than
Explanation of Solution
Calculation:
Calculate the total reaction force.
Here,
Substitute
Therefore the total reaction force is
Write an expression to find the force required to keep the sled and coach in motion.
Here,
Substitute 0.68 for
Therefore, the force required to keep the sled and coach in motion is greater than
Therefore, the force required to keep the sled and coach in motion is greater than
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Chapter 12 Solutions
Basic Biomechanics
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