Chap6 - 2 Strategy The distance is equal to the speed times...

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2. Strategy The distance is equal to the speed times the time interval. Use Eq. (6-1). Solution Find the work done by the rope on the sled. cos cos (240 N)(1.5 m s)(10.0 s)cos30.0 3.1 kJ WF r T v t θθ = Δ = ° = 13. Strategy The kinetic energy of the sack is equal to the work done on it by Sam. Use Eqs. (6-2), (6- 6), and (6-7). Solution (a) Compute the kinetic energy of the sack. 22 2 fi 11 ( ) 0 , so (2.0 N)(0.35 m) 0.70 J . x Km vv m v K W F xK Δ= = −= = = Δ = = (b) Solve for the speed of the sack. 2 1 2 2(0.70 J) 0.37 m s . 2 10.0 kg K v v m == 26. (a) Strategy Use conservation of energy. Solution Find the speed of the cart as it passes point 3. 2 1 2 Em v = if 1 0 y = and 2 333 1 . 2 v m g y =+ f3 3 3i1 1 , so E E mv mgy E E mv + === 2 31 3 2 (20.0 m s) 2(9.81 m s )(10.0 m) 14.3 m s . vvg y =− = = (b) Strategy Use the result of part (a), replacing 3 with 4. If the result is real—the argument of the square root is nonnegative—the cart will reach position 4. Solution Compute the speed of the cart at position 4. 2 41 4 2 (20.0 m s) 2(9.81 m s )(20.0 m) 3 m s y = = The answer is yes; the cart will reach position 4.
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This note was uploaded on 03/01/2009 for the course PHY 2130 taught by Professor Rehse during the Winter '08 term at Wayne State University.

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Chap6 - 2 Strategy The distance is equal to the speed times...

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