PHY231 lecture6

# PHY231 lecture6 - Physic 231 Lecture 6 Main points of...

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Physic 231 Lecture 6 Main points of today’s lecture: Newton’s 3 d Law Frictional forces: – kinetic friction: – static friction xamples N f k k μ = N f s s < Examples.

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Newton’s Third Law When a body exerts a force on another, the second body exerts an equal oppositely directed force on the first body. ote: the two forces act on different bodies Note: the two forces act on different bodies • Force on body 2 ue to body 1: due to body 1: F 21 Force on body 1 due to body 2: F 12 body 1 body 2 3 d law: F 21 =- F 12
Example 1 N 12 N 10 kg 5 kg 60 N 21 A block with mass 5 kg and a second block with mass 10 kg are supported by a frictionless surface. A force of 60 N is applied to the 10 g mass What is the force of the 5 kg block on the 10 kg block? kg mass. What is the force of the 5 kg block on the 10 kg block? x components: (drop subscript x) 21 2 21 12 body 2: N m a; N N == 12 1 12 1 body1:F N ma; F N ma += = + () 21 1 2 1 2 1 F N ma ma ma m m a =+ = + = + F / m m + ( ) 21 aF 12 21 2 2 1 12 NNm F / m m2 0 N N 20N to the left =− + = If objects move together, the relevant mass is their total mass.

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Conceptual question In the 17th century, Otto von Güricke, a physicist in Magdeburg, fitted two hollow bronze hemispheres together and removed the air from the resulting sphere with a pump. Two four-horse teams ould not pull the halves apart even though the hemispheres fell
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PHY231 lecture6 - Physic 231 Lecture 6 Main points of...

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