{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

f5ch08 - CHAPTER 8 CONSERVATION OF ENERGY 199 C HAPTER 8...

Info iconThis preview shows pages 1–4. 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 Document Right Arrow Icon

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

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

Unformatted text preview: CHAPTER 8 CONSERVATION OF ENERGY 199 C HAPTER 8 Answer to Checkpoint Questions . no . , , . ( a ) all tie; ( b ) all tie . ( a ) CD, AB, BC (zero); ( b ) positive direction of x . , , . decrease . ( a ) seventh excited state, with energy E ; ( b ) : eV Answer to Questions . J . ( a ) J; ( b ) J . c and d tie, then a and b tie . ( a ) and ( b ) all tie (same change in elevation) . ( a ) all tie; ( b ) all tie . all tie . ( a ) , , ; ( b ) , , . ( a ) ; ( b ) returns to its starting point and repeats the trip; ( c ) ; ( d ) . less than (smaller decrease in potential energy) . ( a ) increases from zero until shortly after t , then decreases to zero at t ; ( b ) decreases; ( c ) zero until t , then increases until t ; ( d ) constant until t , then decreases until t ; ( e ) zero until t , then increases until t ; ( f ) constant . ( a ) E < J, K < J; ( b ) E < J, K < J . ( a ) AB, CD, and then BC and DE tie (zero force); ( b ) J; ( c ) J; ( d ) J; ( e ) FG; ( f ) DE 200 CHAPTER 8 CONSERVATION OF ENERGY . ( a ) increasing; ( b ) decreasing; ( c ) decreasing; ( d ) constant in AB and BC, decreasing in CD Solutions to Exercises & Problems E As the particle moves from point A to point B , the work W done by F is equal to the loss of the corresponding potential energy of the system: W = U AB = U A U B . Thus U B = U A W = J J = J. E The elastic potential energy stored in the spring is given by U = kx , where k is the spring constant and x is the displacement of the end of the spring from its position when the spring is in equilibrium. Thus k = U x = ( )( J) ( : m) = : N/m : E ( a ) The vertical drop of the book of mass m is h = ( : m : m) = : m. The work done by the weight of the book is W = mgh = ( : kg)( : m/s )( : m) = J. ( b ) The change in the gravitational energy of the textbook-Earth system is related to W by U = W . Thus U = J. ( c ) and ( d ) Denote the potential energy as U when the book is released and as U when it reaches the hands, then U = ( : kg)( : m/s )( : m) = J and U = ( : kg)( : m/s )( : m) = : J. E ( a ) The force of gravity is constant so the work it does is given by W = F d , where F is the force and d is the displacement. The force is vertically downward and has magnitude mg , where m is the mass of the ake, so this reduces to W = mgh , where h is the height from which the ake falls. This is equal to the radius r of the bowl. Thus W = mgr = ( : kg)( : m/s )( : m) = : J : ( b ) The force of gravity is conservative, so the change in gravitational potential energy of the ake-Earth system is the negative of the work done: U = W = : J. CHAPTER 8 CONSERVATION OF ENERGY 201 ( c ) The potential energy when the ake is at the top is greater than when it is at the bottom by j U j . If U = at the bottom, then U = + : J at the top....
View Full Document

{[ snackBarMessage ]}