Ch8_solutions

# Ch8_solutions - (70 kg(2.0 m/s(20 kg 7.0 m/s i f A A B B A...

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P121 Week 3 Homework Solutions so far page 1 of 3 8-1) 8-2) a) 2 2 1 1 2 1 2 1 1 2 2 2 1 1 1 1 1 1 2 m 1 1 final KE = (m + m ) v = (m + m ) v = 2 2 m + m m 1 1 = m v < m v = initial KE m + m 2 2 ! " # \$ % b) There is no external potential energy or external forces that decrease the energy. This means that some energy is lost due to some kind of frictional heating in the collision that has taken place.

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P121 Week 3 Homework Solutions so far page 2 of 3 8-3) b) c) The initial total momentum is i A A B B p m v m v = + Afterwards, they are not moving, so there is no net momentum. 0 f p = The initial and final momenta must be equal.
P121 Week 3 Homework Solutions so far page 3 of 3
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Unformatted text preview: (70 kg)(2.0 m/s) (20 kg) 7.0 m/s i f A A B B A A B B B B p p m v m v m v v m v v = + = = ! = ! = ! d) If they are wearing regular shoes, they will experience a frictional force between their shoes and the floor. This means that the momentum of the father-daughter system does not have to be conserved. In the first scenario, the father could use the friction between his shoes and the floor to push off against his daughter, in which case he may not even move backward. In the second scenario, they could use their shoes to stop themselves from moving, so the initial velocity of the daughter could be anything....
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## This homework help was uploaded on 04/07/2008 for the course PHYS 121 taught by Professor Kernan during the Spring '08 term at Case Western.

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Ch8_solutions - (70 kg(2.0 m/s(20 kg 7.0 m/s i f A A B B A...

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