Falling brick speed - equation needed

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To determine the speed of a brick falling from rest through a distance of 20 meters, the relevant equation is derived from the principles of conservation of energy. The formula v² = u² + 2as applies, where v is the final velocity, u is the initial velocity (0 in this case), a is the acceleration due to gravity (approximately 9.8 m/s²), and s is the distance fallen (20 meters). Substituting the values, the final speed calculates to approximately 19.8 m/s. This approach effectively relates the initial and final energies of the brick during its fall. Understanding these equations is crucial for solving similar physics problems.
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I have a question in my work book that I cannot solve as I can't find the correct equation. The question is:

What speed will the brick have after falling through a distance of 20 metres? U= at rest. There are no other constants given. What equation would I use to solve this problem?

(I have looked in the back of the book and the answer is:19.8 m/s)

Thanks,
Cat.
 
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Think conservation of energy. Compare the initial and final energies at each state and equate them.
 
v**2=u**2+2as
 
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