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PHYSICS 103: Lecture 8

PHYSICS 103: Lecture 8. Agenda for Today:. Review example problems Applications of Newton’s Laws Ramps Circular Motion. Ramps. Why can you lift a very heavy object with a ramp? Why is it easier to lower an object than raise it?

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PHYSICS 103: Lecture 8

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  1. PHYSICS 103: Lecture 8 Agenda for Today: • Review example problems • Applications of Newton’s Laws • Ramps • Circular Motion

  2. Ramps • Why can you lift a very heavy object with a ramp? • Why is it easier to lower an object than raise it? • Why is it more difficult to ride a bike up a steep slope than a more gradual one? FN Ff FN Fg q Fg

  3. We already learned that when all forces balance there is no motion Unbalanced forces induce acceleration

  4. FN = Fg cosq Fg cosq q Fg sinq Forces on a ramp a// = g sinq Fg q

  5. Question:What is the acceleration of a 30 kg block sitting on a frictionless ramp with a 30 degree incline if I apply a 200 N force along the ramp? FN = Fg cosq We know: m = 30 kg a// = g sinq Fg cosq Fg = mg = 30 (9.8) N = 294 N q Fg sinq Fg q a = Fnet/m = 53/30 m/s2 = 1.77 m/s2

  6. Review of Example Problems Distributed in Class:

  7. CENTRIPETAL ACCELERATION Is this object accelerating?

  8. CENTRIPETAL ACCELERATION • Acceleration always points toward center • Acceleration is larger at larger velocities • Acceleration gets larger as radius decreases a=v2/r

  9. Main Points from Today’s Lecture • Applications of Newton’s Laws • Ramps You should understand how to find the net force on an object on a ramp to find the acceleration • Example problems • Centripetal Acceleration/Force • You should understand that anything moving in a circle is accelerating and has a net force on it towards the center of the circle.

  10. HW Study review guide and review all HW and example problems, and go over the relevant sections in the book. Review syllabus on advice on how to do well on tests

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