How Fast Was the Bullet That Hit the Pendulum?

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SUMMARY

The discussion focuses on calculating the speed of a bullet that strikes a ballistic pendulum, specifically a 12.5 g bullet impacting a 2.37 kg pendulum that rises 9.55 cm after the collision. The conservation of momentum and energy principles are applied to solve the problem. The initial momentum of the bullet is equal to the momentum of the bullet-pendulum system immediately after the collision, while the potential energy gained by the pendulum is used to determine the bullet's speed.

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  • Understanding of conservation of momentum
  • Knowledge of conservation of energy principles
  • Familiarity with basic physics equations related to motion
  • Ability to convert units (grams to kilograms, centimeters to meters)
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  • Learn how to calculate potential energy using the formula PE = mgh
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candycooke
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A 12.5 g bullet is shot into a ballistic pendulum that has a mass of 2.37 kg. The pendulum rises a distance of 9.55 cm above its resting position. What was the speed of that bullet?
m(bullet) = 0.0125 kg
m(pendulum) = 2.37 kg
h = 0.0955 m

I know that I'm supposed to use conservation of energy:
P(i)=P(f)
m(1)v(i)=(m(1)+m(2))v(f)

Unfortunately this equation does not take into account how high the pendulum swung, which is obviously an important factor.
 
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Treat this problem as having two parts:
(1) The collision of bullet and pendulum. (What's conserved here?)
(2) The swinging of pendulum+bullet after the collision. (What's conserved here?)
 

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