This preview has intentionally blurred sections. Sign up to view the full version.View Full Document
Unformatted text preview: chaney (glc568) – Laws of Motion – murthy – (21118) 1 This print-out should have 46 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 10.0 points Within a book on a table there are billions of forces pushing and pulling on all of the molecules. Why is it that these forces never by chance add up to a net force in one direction, causing the book to accelerate “spontaneously” across the table? 1. These forces between molecules are much smaller than the friction between the book and the table. 2. These forces are counteracted by grav- ity. 3. The billions of force pairs are internal to the book and exert no net force on the book. correct 4. The forces cause the book to move across the table spontaneously all the time, but the movement is too weak to observe. Explanation: The billions of force pairs are internal to the book, and exert no net force on the book. An external net force is necessary to accelerate the book. 002 10.0 points A heavily loaded freight train moves with constant velocity. What is the relationship between the net force on the first car ( F 1 ) and the net force on the last car ( F 2 )? 1. F 1 > F 2 2. F 1 < F 2 3. Unable to determine. 4. F 1 = F 2 correct Explanation: The net force on each car is zero because the train moves with constant velocity (no acceleration). 003 10.0 points An elevator is being lifted up an elevator shaft at a constant speed by a steel cable as shown in the figure below. All frictional effects are negligible. steel cable Elevator going up at constant speed In this situation, forces on the elevator are such that 1. the upward force by the cable is greater than the sum of the downward force of gravity and a downward force due to the air. 2. the upward force by the cable is greater than the downward force of gravity. 3. None of these. (The elevator goes up because the cable is being shortened, not be- cause an upward force is exerted on the eleva- tor by the cable.) 4. the upward force by the cable is equal to the downward force of gravity. correct 5. the upward force by the cable is smaller than the downward force of gravity. Explanation: Since the elevator is being lifted at a con- stant speed, the net force on it is zero, there- fore, the upward force by the cable is equal to the downward force of gravity. chaney (glc568) – Laws of Motion – murthy – (21118) 2 004 (part 1 of 2) 10.0 points Sue and Jenny kick a soccer ball at exactly the same time. Sue’s foot exerts a force of 41 . 6 N to the north. Jenny’s foot exerts a force of 88 . 6 N to the east. a) What is the magnitude of the resultant force on the ball? Correct answer: 97 . 8801 N....
View Full Document
This note was uploaded on 10/22/2008 for the course PHY 260 taught by Professor Murthy during the Spring '08 term at Kentucky.
- Spring '08