Newton’s Laws The Study of Dynamics. Introduction to Newton’s Laws Newton’s First Law.
Applications of Newton’s Laws Chapter 6 Friction, Strings & Springs Translational Equilibrium...
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Transcript of Applications of Newton’s Laws Chapter 6 Friction, Strings & Springs Translational Equilibrium...
![Page 1: Applications of Newton’s Laws Chapter 6 Friction, Strings & Springs Translational Equilibrium TIMED QUIZ – Monday? Over Force Balances, Free Body Diagrams,](https://reader035.fdocuments.in/reader035/viewer/2022062516/56649dfe5503460f94ae6473/html5/thumbnails/1.jpg)
Applications of Newton’s Laws
Chapter 6Friction, Strings & SpringsTranslational Equilibrium
TIMED QUIZ – Monday?Over Force Balances, Free Body Diagrams, Friction
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Frictional ForcesFriction has its basis in surfaces that are not completely smooth:
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Frictional Forces – Kinetic FrictionKinetic friction: the friction experienced by surfaces sliding against one another
The static frictional force depends on the normal force:
(6-1)
The constant is called the coefficient of kinetic friction.
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Frictional Forces – Kinetic FrictionThe kinetic frictional force is also independent of the relative speed of the surfaces, and of their area of contact.
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The static frictional force keeps an object from starting to move when a force is applied. The static frictional force has a maximum value, but may take on any value from zero to the maximum,
Frictional Forces – Static Friction
depending on what is needed to keep the sum of forces zero.
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Frictional Forces – Static Friction
(6-2)
where
(6-3)
The static frictional force is also independent of the area of contact and the relative speed of the surfaces.
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Example 6-1 in Textbook
• Salt shaker - 50 g• With vo = 1.15 m/s• Stops in 0.840 m• So vf is?
• Value of μk?
• Stopping Δt for different vo?
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Example 6-1 in Textbook
• Part A: Start with Newton’s 2nd Law
• How do you know ax?
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Example 6-1 in Textbook
• Need force balance in y-direction ( for Normal )
• Why do we need the Normal Force on shaker?
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Example 6-1 in Textbook
• Part B: what is the same?
• Use relationship for constant acceleration
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Conceptual Checkpoint
• 6-1 pg 155
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Conceptual Checkpoint 6-1
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Conceptual Checkpoint 6-1
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Homework Problems
• #6, pg 178 ( HONORS )
• #10, pg 178 ( AP )
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Strings and Springs
When you pull on a string or rope, it becomes taut. We say that there is tension in the string.
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Strings and SpringsThe tension in a real rope will vary along its length, due to the weight of the rope.
Here, we will assume that all ropes, strings, wires, etc. are massless unless otherwise stated.
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Strings and Springs
An ideal pulley is one that simply changes the direction of the tension:
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Strings and Springs
Hooke’s law for springs states that the force increases with the amount the spring is stretched or compressed:
The constant k is called the spring constant.
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Translational Equilibrium
When an object is in translational equilibrium, the net force on it is zero:
(6-5)
This allows the calculation of unknown forces.
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Translational Equilibrium
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Conceptual Checkpoint
• 6-2 pg 159• 6-3 pg 162
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Homework Problems
• #22, pg 179