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## Homework Statement

A 25kg box is dropped from a height of 3.5m. Using D'Alembert's Principle work out the velocity reached immediately before hitting the ground.

(Gravity to be taken as 9.81ms-2)

## Homework Equations

KE = (0.5 x (mass x velocity^2))

PE = mass x acceleration due to gravity x height

Final Velocity^2 = Initial Velocity^2 + (2 x Acceleration x Displacement)

## The Attempt at a Solution

I already worked this out using the conservation of energy method and got an answer of Velocity = 8.287ms-1

I then tried playing around with it and realised i could treat it as though it was a box on a horizontal place with no friction

S = 3.5

A = 9.81ms-2

U = 0

V = ?

using v^2 = u^2 + 2as i got the same answer of 8.287ms-1.

This was a guess at a method because its the only other method I've managed to come up with but I'm fairly sure it doesn't use D'Alembert's Principle.

Any help would be appreciated. Thanks guys