Question
How much work is done by the boy pulling his sister 30.0 m in a wagon as shown in Figure 7.36? Assume no friction acts on the wagon.
<b>Figure 7.36</b> The boy does work on the system of the wagon and the child when he pulls them as shown.
Figure 7.36 The boy does work on the system of the wagon and the child when he pulls them as shown.
Question by OpenStax is licensed under CC BY 4.0
Final Answer

1.3×103 J1.3\times 10^{3}\textrm{ J}

Solution video

OpenStax College Physics for AP® Courses, Chapter 7, Problem 6 (Problems & Exercises)

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Video Transcript
This is College Physics Answers with Shaun Dychko. The work done by this brother pulling his sister in the wagon is the component of force that he's applying that's parallel to the displacement multiplied by that displacement. So the force is along this line 30 degrees above horizontal and that means the component that's parallel to the displacement is gonna be this portion here and then we can make a right triangle here and it's the adjacent leg of this right triangle that we are interested in and we can find it by multiplying the hypotenuse by cosine of 30 and so we replace F parallel with F cos of Θ— Θ being this 30 degrees here— and then we multiply that by the displacement. So that's 50 newtons times cos 30 times 30 meters which is 1.3 times 10 to the 3 joules.