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HW3 - Niu(qn269 HW03 Tsoi(58020 This print-out should have...

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Niu (qn269) – HW03 – Tsoi – (58020) 1 This print-out should have 30 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 (part 1 of 3) 10.0 points Consider the following statement made re- garding a book at rest on a level table: The two forces exerted on the book are the normal force directed up and the weight of the book di- rected down. These are equal and opposite to one another. By New- ton’s third law they are an action- reaction pair, so the normal force is always equal to the weight of the book. Do you agree with the statement? 1. Agree; a normal force only exerts enough force to keep the object from falling through. The normal force and weight are always equal, even when other forces are present. 2. Disagree; the weight must be slightly greater than the normal force to keep the book in contact with the table. However, the forces are an action-reaction force pair because they are acting on one object. 3. Disagree; if an additional force acts down on the book, the normal force must also counter this extra force. 4. Agree; for every action there is an equal and opposite reaction (Newton’s third law). Since gravity pulls down on the book, to be “equal and opposite” the force of gravity must equal the normal force. 002 (part 2 of 3) 10.0 points Consider a book on top of a level table while the book is being pressed straight down with a force F by your hand. Book F The following figures show several attempts at drawing free-body diagrams for the book. Which figure has the correct directions for each force? Note: The magnitude of the forces are not necessarily drawn to scale. 1. hand normal gravitational 2. gravitational hand normal 3. normal gravitational hand 4. hand normal gravitational

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Niu (qn269) – HW03 – Tsoi – (58020) 2 5. normal gravitational hand 6. gravitational hand normal 003 (part 3 of 3) 10.0 points What forces change when comparing the free body diagram before the hand was placed on the book to after? 1. normal and F hand 2. F hand 3. gravitational, normal, and F hand 4. gravitational and F hand 5. normal 6. None of these 7. gravitational 8. gravitational and normal 004 (part 1 of 4) 10.0 points A box of mass m with an initial velocity of v 0 slides down a plane, inclined at θ with respect to the horizontal. The coefficient of kinetic friction is μ . The box stops after sliding a distance x . m μ k v 0 θ How far does the box slide? 1. x = v 2 0 g ( μ sin θ 2 cos θ ) 2. x = v 2 0 g ( μ sin θ + cos θ ) 3. x = v 2 0 2 g ( μ sin θ + cos θ ) 4. x = v 2 0 2 g (sin θ μ cos θ ) 5. x = v 2 0 2 g sin θ 6. x = v 2 0 2 g ( μ cos θ sin θ ) 7. x = v 2 0 g (sin θ μ cos θ ) 8. x = v 2 0 2 g μ cos θ 9. x = v 2 0 2 g ( μ cos θ + sin θ ) 10. x = v 2 0 2 g ( μ sin θ cos θ ) 005 (part 2 of 4) 10.0 points How much work is done by friction?
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