What is the speed of the bullet in a ballistic pendulum collision?

AI Thread Summary
The discussion focuses on calculating the speed of a bullet in a ballistic pendulum scenario, where a 16g bullet collides with a 1.5kg pendulum bob. The participant initially uses the conservation of momentum and energy equations to find the bullet's speed, arriving at an incorrect value due to a miscalculation of mass. After realizing the error in the mass used in the final computation, the correct approach involves recalculating using the accurate mass of the pendulum bob. The correct bullet speed is ultimately derived from the corrected calculations. The conversation highlights the importance of careful arithmetic in physics problems.
nns91
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Homework Statement



A 16g bullet is fired into the bob of a ballistic pendulum of mass 1.5kg When the bob is at its maximum height, the strings make an angle of 60 degree with the vertical. The length of the pendulum is 2.3 m. Find the speed of the bullet.

Homework Equations



pi=pf

The Attempt at a Solution



So I think it is an inelastic collision so vf = (mbullet*vbullet) / (mbullet+mblock)

After collision:

(1/2)*(mbullet+mblock)vf2 = (mbullet+mblock)*g*h

h=2.3-2.3*cos60=1.15m

then I solved for vf2=2*9.981*1.15=22.563

the I substitute into the first formula ( I actually squared both sides to use vf^2) to find vbullet= 346.2 m/s. However it is wrong. Where did I do wrong ??
 
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Your method looks perfect. Check your arithmetic in your last step.
 
Cool. I found out that I got the wrong mass for the last computation, I put in 1.15 instead of 1.5
 
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