Homework-6-soln

Homework-6-soln - Homework Week 6 Chapter 7 SOLUTIONS 1(7.2 Children in a tree house lift a small dog in a basket 4.70 m up to their house If it

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Homework: Week 6 – Chapter 7 – SOLUTIONS 1. (7.2) Children in a tree house lift a small dog in a basket 4.70 m up to their house. If it takes 201 J of work to do this, what is the combined mass of the dog and basket? SOLUTION W = Fd = mgd ( ) 2 m s 201 J 9.81 (4.70 m) 4.36 kg W m gd = = = 2. (7.12) Water skiers often ride to one side of the center line of a boat, as shown in the figure above. In this case, the ski boat is traveling at 15 m/s and the tension in the rope is 75 N. If the boat does 3500 J of work on the skier in 50.0 m, what is the angle θ between the tow rope and the center line of the boat? SOLUTION W = ( T cos θ ) d cos W Td = 1 1 cos 3500 J cos (75 N)(50.0 m) 21 W Td = = 3. (7.20) At t = 1.0 s, a 0.40-kg object is falling with a speed of v = 6.0 m/s. At t = 2.0 s it has a kinetic energy of 25 J. (a) What is the kinetic energy of the object at t = 0.5 s? (b) What is the speed of the object at t = 1.0 s? (c) How much work was done on the object between t = 0.5s and t = 1.0 s? SOLUTIONS (a) 2 2 11 m (0.40 kg) 6.0 7.2 J 22 s Km v ⎛⎞ == = ⎜⎟ ⎝⎠ (b) 2 1 2 K mv = 2 2 2 2(25 J) 11 m/s 0.40 kg K v m = (c) 21 25 J–7.2 J 18 J WKKK =∆ = = =
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4. (7.24) A 65-kg bicyclist rides his 10.0-kg bicycle with a speed of 12 m/s.
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This note was uploaded on 07/02/2011 for the course PHYS 201 taught by Professor Woodahl during the Fall '09 term at Indiana.

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Homework-6-soln - Homework Week 6 Chapter 7 SOLUTIONS 1(7.2 Children in a tree house lift a small dog in a basket 4.70 m up to their house If it

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