October 17 Solutions - 8.3. IDENTIFY and SET UP: EXECUTE:...

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8.3. IDENTIFY and SET UP: p mv . 2 1 2 K mv . EXECUTE: (a) p v m and 2 2 1 2 2 pp Km mm . (b) cb KK and the result from part (a) gives 22 . b b c c c c 0.145 kg 1.90 0.040 kg m p p p p m . The baseball has the greater magnitude of momentum. / 0.526 . (c) 2 2 p mK so mw gives m m w w m K m K . w mg , so m m w w w K w K . m w m m m w 700 N 1.56 450 N w K K K K w . The woman has greater kinetic energy. / 0.641 . 8.12. IDENTIFY: Apply Eq. 8.9 to relate the change in momentum of the momentum to the components of the average force on it. SET UP: Let + x be to the right and + y be upward. EXECUTE: (a) 21 (0.145 kg)( [65.0 m/s]cos30 50.0 m/s) 15.4 kg m/s x x x x J p mv . (0.145 kg)([65.0 m/s]sin30 0) 4.71 kg m/s y y y y J p mv mv The horizontal component is 15.4 kg m/s , to the left and the vertical component is 4.71 kg m/s , upward. (b) av- 3 15.4 kg m/s 8800 N 1.75 10 s x x J F t . av- 3 4.71 kg m/s 2690 N y y J F t . The horizontal component is 8800 N, to the left, and the vertical component is 2690 N, upward. EVALUATE: The ball gains momentum to the left and upward and the force components are in these directions. 8.16. IDENTIFY: Apply conservation of momentum to the system of you and the ball. In part (a) both objects have
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