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Chapter%206%20Homework (8)

# Chapter%206%20Homework (8) - 26 A 75.0-kg ice skater moving...

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26. A 75.0-kg ice skater, moving at 10.0 m/s, crashes into a stationary skater of equal mass. After the collision, the two skaters move as a unit at 5.00 m/s. Suppose the average force a skater can experience without breaking a bone is 4 500 N. If the impact time is 0.100 s, does a bone break? 6.26 For each skater, the impulse-momentum theorem gives () ( ) ( ) 75.0 kg 5.00 m s 0.100 s p mv F tt Δ Δ == = = ΔΔ 3 3.75 10 N × . Since 4500 N F < , there are no broken bones . 27. A railroad car of mass 2.00 x 10 4 kg moving at 3.00 m/s collides and couples with two coupled railroad cars, each of the same mass as the single car and moving in the same direction at 1.20 m/s. (a) What is the speed of the three coupled cars after the collision? (b) How much kinetic energy is lost in the collision? 6.27 (a) If M is the mass of a single car, conservation of momentum gives ( ) ( ) ( ) ( ) 3 3.00 m s 2 1.20 m s f Mv M M =+ , or f v = 1.80 m s (b) The kinetic energy lost is lost i f K EK E K E = , or 22 11 1 3.00 m s 2 1.20 m s 3 1.80 m s 2 lost KE M M M 2 With , this yields 4 2.00 10 kg M lost = 4 2.16 10 J × .

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Chapter%206%20Homework (8) - 26 A 75.0-kg ice skater moving...

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