exam01_sol_f06 - 1 MASSACHUSETTS INSTITUTE OF TECHNOLOGY...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: 1 MASSACHUSETTS INSTITUTE OF TECHNOLOGY Department of Physics Physics 8.01 Fall Term 2006 Exam 1 Solutions Part I Concept Questions: (20 points). Circle your answer. There are five questions and each question is worth 4 points. 1) (4 points) A pendulum bob swings down and is moving fast at the lowest point in its swing. T is the tension in the string, T ! W = mr " 2 W is the gravitational force exerted on the pendulum bob. Which free-body diagram below best represents the forces exerted on the pendulum bob at the lowest point? The lengths of the arrows represent the relative magnitudes of the forces. Solution: d). The bob is undergoing circular motion. It is accelerating towards the center. Newton’s Second Law gives T ! W = mr " 2 hence T = W + mr ! 2 so T > W . 2 2) (4 points) Which of the following expressions gives a reasonable formula for the period of the moon orbiting around the earth? Let G be the universal gravitational constant, r e , m be the average distance between the earth and the moon, m m be the mass of the moon, and m e be the mass of the earth. a) T ! G m e m m / r e , m 2 . b) T ! G m e m m / r e , m . c) T ! r e , m 3 / Gm m . d) T ! r e , m 3 / Gm e . e) T ! r e , m 2 / Gm e . f) T ! r e , m 2 / Gm m . Solution: (d). The answer cannot depend on mass of the moon by the Equivalence Principle (the moon’s mass cancels from each side of Newton’s second Law). The period must be some product of the given T ! r e , m a G b m e c dim[ G ] = dim[force ! m 2 ! kg-2 ] = dim[kg ! m ! s-2 ! m 2 ! kg-2 ] = dim[s-2 ! m 3 ! kg-1 ] dim[ m e ] = kg dim[( r e , m 3 / Gm e...
View Full Document

This note was uploaded on 10/15/2011 for the course PHYSICS 0207239 taught by Professor Mamar during the Spring '09 term at Jordan University of Science & Tech.

Page1 / 14

exam01_sol_f06 - 1 MASSACHUSETTS INSTITUTE OF TECHNOLOGY...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online