Ch4-HW3-solutions

# Ch4-HW3-solutions - louey(cal2859 – Ch4-HW3 – florin...

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Unformatted text preview: louey (cal2859) – Ch4-HW3 – florin – (56930) 1 This print-out should have 23 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 (part 1 of 4) 10.0 points When you apply a horizontal force of 80 N to a block, the block moves across the floor at a constant speed ( μ k = μ s ). What happens if instead you apply a force of 60 N? 1. The block will not move. correct 2. The block will move at a slower constant speed. 3. The box will accelerate, but slowly. 4. The block will start to move, but its speed will decrease. Explanation: The force is less than the maximum force of static friction. This implies that the block remains at rest. 002 (part 2 of 4) 10.0 points When you apply a force of 60 N, what is the magnitude of the horizontal component of the force that the floor exerts on the block? Correct answer: 60 N. Explanation: Since the block isn’t moving (static), the forward force on the block must be nulled out by the force on the block by the floor. Thus, the floor exerts a horizontal force of magnitude 60 N. 003 (part 3 of 4) 10.0 points What happens if instead you exert a force of 100 N? 1. The box will move at a larger constant speed. 2. The box will continue to sit still. 3. The box will start to move, but will even- tually slow down. 4. The box will accelerate. correct Explanation: In this case the block will accelerate at a constant rate: a = F applied − F max , friction M . 004 (part 4 of 4) 10.0 points When you apply a force of 100 N, what is the magnitude of the horizontal component of the force that the floor exerts on the block? Correct answer: 80 N. Explanation: In this case the horizontal component of the force the floor exerts is 80 N, since this is the maximum force of kinetic friction it can exert. 005 (part 1 of 3) 10.0 points Bob is pushing a box of mass 5 kg across the floor at a constant speed of 1 m / s, applying a horizontal force whose magnitude is 24 N. Al- ice is pushing an identical box across the floor at a constant speed of 4 m...
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Ch4-HW3-solutions - louey(cal2859 – Ch4-HW3 – florin...

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