HW_7_solutions

# HW_7_solutions - Solutions HW#7 Sprin 07, P112 1. Calculate...

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Solutions HW#7 Sprin 07, P112 1. Calculate the spring constant k=F/x=800N/0.2m=4000N/m. a)The potential energy stored in a stretched spring is PE=1/2kx 2 =(0.5)(4000N/m)(0.2m) 2 =80J. b) PE=1/2kx 2 =(0.5)(4000N/m)(0.05m) 2 =5J. 2 . Let the y + direction be up. kg 80 . 4 = m . 0 i = v r . j r ˆ ) m 0 . 25 ( ! = " r . (a) J 10 18 . 1 ) m 0 . 25 )( m/s 81 . 9 )( kg 80 . 4 ( ) ˆ ( 3 2 g ! = = " # \$ = r j r mg W . (b) J 10 18 . 1 J 10 18 . 1 0 3 3 g i tot i f ! = ! + = + = + = W K W K K . (c) 2 f 2 1 f mv K = . m/s 1 . 22 2 f f = = m K v . 3 . We can calculate the magnitude of F from the components: F = F x 2 + F y 2 F x = " U x = # kx F y = U y = # ky F = k x 2 + y 2 = kr where r is the particles distance from the origin. 4. Kinetic energy is calculated by KE=1/2mv 2 , so we need to estimate the mass of the continent. The velocity (drift rate) is given as 1cm/year, or v=0.01m/(3.1x10 7 s)=3.2x10 -10 m/s. Mass is given as density times volume. The volume can be estimated by the

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## This note was uploaded on 03/27/2008 for the course PHYS 1112 taught by Professor Leclair,a during the Spring '07 term at Cornell University (Engineering School).

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HW_7_solutions - Solutions HW#7 Sprin 07, P112 1. Calculate...

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