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Physics · WORK, ENERGY AND POWER
हिन्दीA woman pushes a crate on a rough floor. For the first \( 12\text{ m} \), she applies a constant force of \( 120\text{ N} \). Over the next \( 8\text{ m} \), her applied force decreases linearly to \( 40\text{ N} \). Throughout the motion, an opposing frictional force of \( 60\text{ N} \) acts on the crate. The net work done on the crate during the entire \( 20\text{ m} \) displacement is:
Correct answer · Option 2
\( 880\text{ J} \)
Explanation
Work done by applied force \( W_F = (120 \times 12) + \frac{1}{2}(120 + 40)(8) = 1440 + 640 = 2080\text{ J} \). Work done by friction \( W_f = -60 \times 20 = -1200\text{ J} \). Net work \( W_{\text{net}} = 2080 - 1200 = 880\text{ J} \).
