How Fast Were the Catapulted Boulders Initially?

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SUMMARY

The discussion focuses on calculating the initial velocity of boulders catapulted from below a castle wall, given a final vertical velocity of 9.2 m/s and a height of 40 m. The relevant equation used is Δd = vf² - vi² - 2a, where 'a' represents the acceleration due to gravity (9.8 m/s²). The solution indicates that the initial velocity (vi) is determined to be -10.4 m/s, which suggests a downward motion. The equation vf² = vi² - 2g(Δd) is also referenced for clarity.

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Homework Statement



A knight sits on a castle wall during a siege.
To while away the time, he notes that boulders catapulted from below land on the top of
his wall with a vertical velocity of 9.2 m/s.
If he is 40 m above the catapult, what
is the initial velocity of the boulders? The
acceleration of gravity is 9.8 m/s^2

Answer in units of m/s

Homework Equations


Δd=v^2f-v^2i-2a

The Attempt at a Solution


-10.4
 
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Casey314stl said:

Homework Statement



A knight sits on a castle wall during a siege.
To while away the time, he notes that boulders catapulted from below land on the top of
his wall with a vertical velocity of 9.2 m/s.
If he is 40 m above the catapult, what
is the initial velocity of the boulders? The
acceleration of gravity is 9.8 m/s^2

Answer in units of m/s

Homework Equations


Δd=v^2f-v^2i-2a

The Attempt at a Solution


-10.4
What equation is that ?

vf2 = vi2 -2g(Δd)
 

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