You have a bullet that has a mass of 21 grams and a combined mass of bullet + pe

Question

You have a bullet that has a mass of 21 grams and a combined mass of bullet + pendulum bob of 212grams. After you fire your bullet, your pendulum rises by an amount hf?hi= 8.6 cm.

A. What is the speed of the bullet + pendulum bob unit right after they collide?

Express your answer in meters per second, to 3 significant figures.

B. At what velocity was the bullet fired by the gun?

Express your answer in meters per second, to 3 significant figures.

C. Was kinetic energy conserved?

- No, due to large experimental errors. - Yes, the two numbers come out equal. - No, as expected in an inelastic collision. - Yes, within experimental uncertainties.

Explanation / Answer

The speed of the bullet and pendulum bob is given by v =Sqrt(2gh) =Sqrt(2*9.81*0.086) =1.298m/s2

According the law of conservation of momentum

Pbullet+Pbob =Psystem

mvbullet=(M+m)Sqrt(2gh)

Therefore the velocity of the bullet is vbullet =[(M+m)m]Sqrt(2gh) =[0.212+0.021/0.021](Sqrt(2*9.81*0.086))=(11.095)(1.298)=144.12cm/s2 =14.401m/s2

c)

Yes, the kinetic energy is conserved.within experimetal uncertainties.

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