Work, Power and EnergyMedium

Question

A body of mass 1 kg moves along a straight line with a velocity $v = 2x^{2}$. The work done by the body during displacement from $x = 0$ to 5 m is $\_\_\_\_$ J.

Options

A.0
B.250
C.1250
D.1000

Solution

Sol. [Key Concept: Work done $= \Delta\ KE = \frac{1}{2}\ m(v_{f}^{2} - v_{i}^{2})$ with $v = 2x^{2}$ evaluated at $x = 0$ and $x = 5$.]

$$w.\Delta = \Delta K.E$$

$$\begin{matrix} & \ = \frac{1}{2}\text{ }m\left( v_{f}^{2} - v_{i}^{2} \right) \\ & \ = \frac{1}{2} \times 1\left\lbrack \left( 2(5)^{2} \right)^{2} - (2(0))^{2} \right\rbrack^{0} \\ & \ = \frac{1}{2} \times 50 \times 50 = 1250\text{ }J \end{matrix}$$

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