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Unformatted text preview: 1 Physics 1D03 - Lecture 7 Newton’s Laws (II) Newton’s Laws (II) • Free-body diagrams • Normal Force, ropes and pulleys, friction Serway and Jewett : 5.7, 5.8 Practice: Chapter 5, problems 25, 29, 30, 33 Physics 1D03 - Lecture 7 Free-Body Diagrams • Pick one object (the “body”). • Draw all external forces which act directly on that body (gravity, contact, electromagnetic). Imagine cutting around the body to separate it from its surroundings. Replace each external object with a force applied at the point of contact. • Indicate the direction of the acceleration of the object beside the diagram; but remember, m a is not a force. 2 Physics 1D03 - Lecture 7 Example: free-body diagram A block is pulled up a frictionless ramp: m Note : • title, to indicate the chosen object • contact forces, to replace the rope and the ramp • gravity doesn’t require contact • a may be indicated for reference, but is not a force g m r T F r n r a r Forces on Block Physics 1D03 - Lecture 7 Ropes and Pulleys • Tension is uniform in a rope of negligible mass...
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