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Unformatted text preview: madrid (tmm2353) – HW 4-3 – Antoniewicz – (56445) 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) 2.0 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 start to move, but its speed will decrease. 3. The box will accelerate, but slowly. 4. The block will move at a slower constant speed. 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) 2.0 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) 2.0 points What happens if instead you exert a force of 100 N? 1. The box will continue to sit still. 2. The box will move at a larger constant speed. 3. The box will accelerate. correct 4. The box will start to move, but will even- tually slow down. Explanation: In this case the block will accelerate at a constant rate: a = F applied − F max , friction M . 004 (part 4 of 4) 2.0 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) 3.0 points Bob is pushing a box of mass 5 kg across the floor at a constant speed of 3 m / s, applying a horizontal force whose magnitude is 24 N. Al- ice is pushing an identical box across the floor...
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This note was uploaded on 11/15/2011 for the course PHY 303K taught by Professor Turner during the Fall '08 term at University of Texas.
- Fall '08