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PH101 HW Energy 1

PH101 HW Energy 1 - This print-out should have 23 questions...

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This print-out should have 23 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 10.0 points Potential energy and kinetic energy are forms of what kind of energy? 1. heat 2. chemical 3. mechanical correct 4. nuclear 5. electromagnetic Explanation: 002 (part 1 of 2) 10.0 points If a golf ball and a ping-pong ball both move with the same kinetic energy, which has the greater speed? 1. the golf ball 2. Cannot be determined 3. The two balls have the same speed. 4. the ping-pong ball correct Explanation: Kinetic energy is 1 2 m v 2 . Since they have the same kinetic energy, 1 2 m g v 2 g = 1 2 m p - p v 2 p - p . Since m g > m p - p , it follows that v g < v p - p . 003 (part 2 of 2) 10.0 points In a gaseous mixture of massive molecules and light molecules with the same average KE, which have the greater speed? 1. They have the same speed. 2. the massive molecules 3. the light molecules correct 4. Cannot be determined Explanation: Since m massive > m light , v massive < v light . 004 10.0 points Does the KE of a car change more when it accelerates from 27 km / h to 37 km / h or when it accelerates from 37 km / h to 47 km / h? 1. More information is needed. 2. From 37 km / h to 47 km / h correct 3. No di ff erence 4. From 27 km / h to 37 km / h Explanation: The change in kinetic energy is 1 2 m v 2 f - 1 2 m v 2 i , so we are comparing v 2 f - v 2 i . (47 km / h) 2 - (37 km / h) 2 = 840 km 2 / h 2 is larger than (37 km / h) 2 - (27 km / h) 2 = 640 km 2 / h 2 , so KE changes more for a given Δ v at the higher speeds. 005 (part 1 of 5) 10.0 points A 15 . 7 kg block is dragged over a rough, hor- izontal surface by a constant force of 148 N acting at an angle of angle 34 . 1 above the horizontal. The block is displaced 75 . 8 m, and the coe ffi cient of kinetic friction is 0 . 194. 15 . 7 kg μ = 0 . 194 148 N 34 . 1

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Find the work done by the 148 N force. The acceleration of gravity is 9 . 8 m / s 2 .
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