From Mechanics

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Revision as of 09:46, 30 September 2010

As the brick has no speed at the start

\displaystyle \text {KE = KE gained}.

Using Energy lost due to friction = Work done against friction we get,

\displaystyle \begin{align} & \text{PE lost - KE gained = Work done against friction} \\ & \\ & \text{which}\ \text{gives} \\ & \\ & \text{KE = KE gained = PE lost - Work done against friction} \\ \end{align}

\displaystyle \begin{align} & KE=\text{2}\times \text{9}\text{.8}\times \text{3}.2-1\text{0}\times \text{3}\text{.2}=\text{30}\text{.72 J} \\ & \\ & \frac{\text{1}}{\text{2}}\times 2{{v}^{2}}=30\textrm{.}72 \\ & v=5\textrm{.}54\text{ m}{{\text{s}}^{\text{-1}}} \end{align}