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Unformatted text preview: 1 Physics 1D03 - Lecture 7 Newtons Laws (II) Newtons Laws (II) Free-body diagrams Normal Force, ropes and pulleys, friction Serway and Jewett : 5.7, 5.8 Practice: Chapter 5, problems 20, 25, 27, 57, 69. 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. 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 doesnt 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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