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PHY183-Lecture09

# PHY183-Lecture09 - 1 Physics for Scientists& Physics for...

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Unformatted text preview: 1 Physics for Scientists & Physics for Scientists & Engineers 1 Engineers 1 Physics for Scientists & Physics for Scientists & Engineers 1 Engineers 1 February 1, 2011 Physics for Scientists&Engineers 1 1 Spring Semester 2011 Lecture 9 Force 2 Clicker Quiz Clicker Quiz Clicker Quiz Clicker Quiz s Chapter 4 discusses which equation A . E = m c 2 B . F = m a C . p V = n R T D . p = m v E . K = (1/2) m v 2 February 1, 2011 Physics for Scientists&Engineers 1 2 3 Forces and Dynamics Forces and Dynamics Forces and Dynamics Forces and Dynamics s Forces that act on objects and Newton’s Laws February 1, 2011 Physics for Scientists&Engineers 1 3 4 Types of Forces Types of Forces Types of Forces Types of Forces s Contact force • Tension • Compression • Normal force (perpendicular) • Friction force pring force s Spring force • A force is needed to stretch or compress a spring • Has the special property that it depends linearly on the change in length of the spring February 1, 2011 Physics for Scientists&Engineers 1 4 5 Fundamental Forces Fundamental Forces Fundamental Forces Fundamental Forces s All the forces on the previous slide are manifestations of the four fundamental forces • Gravitational force • When you hold an object in the air and release it, it falls to the ground • Electromagnetic force • Repulsion of like electric charges • Attraction of opposite magnetic poles • Strong nuclear force • Holds atomic nuclei together • Weak nuclear force • Responsible for the decay the neutron February 1, 2011 Physics for Scientists&Engineers 1 5 Don't affect our everyday lives 6 Ways to Use Forces Ways to Use Forces Ways to Use Forces Ways to Use Forces February 1, 2011 Physics for Scientists&Engineers 1 6 7 Gravitational Force Vector Gravitational Force Vector Gravitational Force Vector Gravitational Force Vector s Forces have a direction s If you hold a laptop in your hand, you can tell that the ravitational gravitational force points downward (- y direction) February 1, 2011 Physics for Scientists&Engineers 1 7 = - = a g ˆ g g F F y F m g 8 Weight and Mass Weight and Mass Weight and Mass Weight and Mass s Magnitude of gravitational force on an object = weight s Gravitational force on an object, F g , is always proportional to its mass s Near surface of Earth (altitude of 10 km or less): eight is constant and is the product of object’s February 1, 2011 Physics for Scientists&Engineers 1 8 Weight is constant and is the product of object’s mass and the Earth’s gravitational acceleration: F g = mg g = 9.81 m/s 2 9 s Example: • Object with mass m = 5.00 kg • Gravitational force F g = mg = (5.00 kg)(9.81 m/s 2 ) = 49.05 kg m/s 2 s Force Unit 1 kg m/s 2 = 1 N Weight and Mass Weight and Mass Weight and Mass Weight and Mass...
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PHY183-Lecture09 - 1 Physics for Scientists& Physics for...

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