Question:

A body of mass 1 kg starts moving from rest under the action of a force which varies with displacement as $F=2x+5$ (in newtons). The work done by this force to displace the body from $x=0$ to $x=2$ m is:

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For linear force $F=mx+c$, Work is also (Average Force $\times$ Displacement). $F_{avg} = (5 + 9)/2 = 7$; $W = 7 \times 2 = 14$ J.
  • 8 J
  • 10 J
  • 12 J
  • 14 J
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The Correct Option is D

Solution and Explanation


Step 1: Concept

Work done by a variable force is given by $W = \int F dx$.

Step 2: Meaning

Integrate the force function $F=2x+5$ from the limits $x=0$ to $x=2$.

Step 3: Analysis

$W = \int_{0}^{2} (2x+5) dx = [x^2 + 5x]_{0}^{2} = (2^2 + 5(2)) - (0)$.

Step 4: Conclusion

$W = 4 + 10 = 14$ J.
Final Answer: (D)
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