PH101 HW Energy 1

PH101 HW Energy 1 - This print-out should have 23 questions Multiple-choice questions may continue on the next column or page nd all choices before

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This print-out should have 23 questions. Multiple-choice questions may continue on the next column or page – fnd 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 mv 2 .S i n c et h e yh a v e 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 ,itFo l lowsthat 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 light ,v massive light . 004 10.0 points Does the KE oF a car change more when it accelerates From 27 km / hto37km / horwhen it accelerates From 37 km / hto47km / h? 1. More inFormation is needed. 2. ±rom 37 km / / h correct 3. No di²erence 4. ±rom 27 km / / h Explanation: The change in kinetic energy is 1 2 2 f - 1 2 2 i , so we are comparing v 2 f - v 2 i . (47 km / h) 2 - (37 km / h) 2 =840km 2 / h 2 is larger than (37 km / h) 2 - (27 km / h) 2 =640km 2 / h 2 , so KE changes more For a given Δ v at the higher speeds. 005 (part 1 oF 5) 10.0 points A15 . 7kgb lockisdraggedoverarough ,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 . 8m , and the coe³cient oF kinetic Friction is 0 . 194. 15 . 7kg 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 . 8m / s 2 . Correct answer: 9289 . 51 J. Explanation: Consider the force diagram F θ mg n f k Work is ± W = ± F · ±s ,where is the distance traveled. In this problem =5ˆ x is only in the ˆ x direction.
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This note was uploaded on 10/03/2010 for the course PH 101 taught by Professor Jones,s during the Spring '08 term at Alabama.

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PH101 HW Energy 1 - This print-out should have 23 questions Multiple-choice questions may continue on the next column or page nd all choices before

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