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Unformatted text preview: 1) a net force acted on it 2) no net force acted on it 3) it remained at rest 4) it did not move, but only seemed to 5) gravity briefly stopped acting on it ConcepTest ConcepTest 4.1c 4.1c Newton Newton ’s First Law III s First Law III You put your book on the bus seat next to you. When the bus stops suddenly, the book slides forward off the seat. Why? 1) a net force acted on it 2) no net force acted on it 3) it remained at rest 4) it did not move, but only seemed to 5) gravity briefly stopped acting on it The book was initially moving forward (since it was on a moving bus). When the bus stopped, the book continued moving forward continued moving forward , which was its initial state initial state of motion of motion , and therefore it slid forward off the seat. ConcepTest ConcepTest 4.1c 4.1c Newton Newton ’s First Law III s First Law III You put your book on the bus seat next to you. When the bus stops suddenly, the book slides forward off the seat. Why? Followup: Followup: What is the force that usually keeps the book on the seat? What is the force that usually keeps the book on the seat? ConcepTest ConcepTest 4.4a 4.4a Off to the Races I Off to the Races I 1) 16 s 2) 8 s 3) 4 s 4) 2 s 5) 1 s From rest, we step on the gas of our Ferrari, providing a force F for 4 secs , speeding it up to a final speed v . If the applied force were only 1/2 F , how long would it have to be applied to reach the same final speed? v F In the first case, the acceleration acts over time T = 4 s T = 4 s to give velocity v = a = a T . In the second case, the force is half half , therefore the acceleration is also half half , so to achieve the same final speed , the time must be doubled time must be doubled . ConcepTest ConcepTest 4.4a 4.4a Off to the Races I Off to the Races I 1) 16 s 2) 8 s 3) 4 s 4) 2 s 5) 1 s From rest, we step on the gas of our Ferrari, providing a force F for 4 secs , speeding it up to a final speed v . If the applied force were only 1/2 F , how long would it have to be applied to reach the same final speed? v F From rest, we step on the gas of our Ferrari, providing a force F for 4 secs . During this time, the car moves 50 m . If the same force would be applied for 8 secs , how much would the car have traveled during this time?...
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This note was uploaded on 05/13/2010 for the course PHYSICS 53L taught by Professor Mueller during the Fall '07 term at Duke.
 Fall '07
 Mueller
 Physics, Force

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