Conservation of momentum: vertical shot

[mandy9008]

Homework Statement

A 0.028 kg bullet is fired vertically at 165 m/s into a 0.15 kg baseball that is initially at rest. How high does the combined bullet and baseball rise after the collision, assuming the bullet embeds itself in the ball?

Homework Equations

mv + mv = mv + mv

The Attempt at a Solution

m1 = 0.028 kg
v1 = 165 m/s
m2 = 0.15 kg
v2i = 0 m/s

(0.028 kg)(165 m/s) + (0.15 kg)(0 m/s) = (0.178 kg) vf
vf=25.96 m/s

v²=vo² - 2gy
25.96² = - 2(9.8 m/s²)y
y=693.5m

 

[rock.freak667]

v²=vo² - 2gy
25.96² = - 2(9.8 m/s²)y
y=693.5m

That does not give 693.5 m. Recheck it.

 

[mandy9008]

ah, i subtracted instead of divided. man, i feel silly now! thank you! when I divided, i got 34.4m, which is correct :)