Homework-8-soln

Homework-8-soln - Homework: Week 8 Chapter 9 SOLUTIONS 1....

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Homework: Week 8 – Chapter 9 – SOLUTIONS 1. (9-6) A 220-g ball falls vertically downward, hitting the floor with a speed of 2.5 m/s and rebounding upward with a speed of 2.0 m/s. (a) Find the magnitude of the change in the ball’s momentum. (b) Find the change in the magnitude of the ball’s momentum. (c) Which of the two quantities calculated in parts (a) and (b) is more directly related to the net force acting on the ball during its collision with the floor? SOLUTIONS (a) fi () mm ˆˆ (0.220 kg) 2.0 2.5 ss m ˆ (0.220 kg) 4.5 s m ˆ 0.99 kg s 0.99 kg m s m p ∆= =− ⎡⎤ ⎛⎞ ⎜⎟ ⎢⎥ ⎝⎠ ⎣⎦ = =⋅ pp p vv yy y y GG G GG (b) ( ) (0.220 kg) 2.0 2.5 0.11 kg m s ppm −= = (c) 2. (9-10) A 0.50-kg croquet ball is initially at rest on the grass. When the ball is struck by a mallet, the average force exerted on it is 230 N. If the ball’s speed after being struck is 3.2 m/s, how long was the mallet in contact with the ball? SOLUTION av m s av (0.50 kg) 3.2 0 7.0 ms 230 N p F t p t F = = = 3. (9-24) Suppose the car in the figure below (initially traveling in the x- direction, with mass 950 kg) has an initial speed of 20 m/s, and that the direction of the wreckage after the collision is 40.0 o above the x axis. Find the initial speed of the minivan (initially traveling in the y-direction, with a mass of 1300 kg) and the final speed of the wreckage.
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SOLUTION 22 11 tan mv θ = () m s 2 2 (950 kg) 20.0 tan 40.0 tan 12 m s 1300 kg v m ° == = and ( ) m s f 12 (950 kg) 20.0 11 m s ( )cos (950 kg 1300 kg)cos 40.0 v mm = ++ ° 4. (9-28) A 0.470-kg block of wood hangs from the ceiling by a string, and a 0.0700-kg wad of putty is thrown straight upward, striking the bottom of the block with a speed of 5.60 m/s. The wad of putty
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Homework-8-soln - Homework: Week 8 Chapter 9 SOLUTIONS 1....

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