7.2 Problems 7) A 0.330-kg volleyball is thrown vertically downward with a speed

Question

7.2 Problems 7) A 0.330-kg volleyball is thrown vertically downward with a speed of 0.150 m/s in a place where g = 9.81 m/s^2. It takes it 0.0655 s to reach the ground. What is the magnitude of its momentum just before it hits the ground? A) 0.212 kg m/s B) 0.262 kg m/s C) 0.163 kg m/s D) 0.0216 kg m/s E) 0.0418 kg m/s 8) In a police ballistics test, 2.00-g bullet traveling at 700 m/s suddenly hits and becomes embedded in a stationary 5 00.kg wood block. What is the final speed of the combined block and bullet immediately following the collision? 9) A 328-kg car moving at 19.1 m/s in the +x direction hits from behind a second car moving at 130 m/s in the same direction. It the second car has a mass of 790 kg and a speed of 15.1 m/s right after the collision, what is the velocity of the first car after this sudden collision? A) 14.0 m/s B) 18.2 m/s C) 24.2 m/s D) -14.0 m/s

Explanation / Answer

Number 7)

Find the velocity just before it hits the ground...

vf = vo + at

vf = (.150) + (9.81)(.0655)

vf = .793 m/s

p = mv

p = (.33)(.793)

p = .262 kg m/s (Choice B)

Number 8)

By conservation of momentum...

mv = (m + m)(v)

(.002)(700) = (5.002)(v)

v = .280 m/s

Number 9)

By conservation of momentum

mv + mv = mv + mv

(328)(19.1) + (790)(13) = (328)(v) + (790)(15.1)

v = 14.0 m/s (Choice A)

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