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Question

A landscaper is easing a wheelbarrow full of soil down a hill. Define the system you would analyze and list all the forces that you would need to include to calculate the acceleration of the wheelbarrow.

Question by OpenStax is licensed under CC BY 4.0.
Final Answer

System includes the gardener, wheel barrow, and soil. See solution video for the free body diagram.

Solution Video

OpenStax College Physics Solution, Chapter 4, Problem 13 (Test Prep for AP® Courses) (1:35)

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Video Transcript
ed1ch04ap13 This is College Physics Answers with Shaun Dychko. The system we would analyze here is a combination of the gardener, the wheelbarrow and the soil in the wheelbarrow. We have to consider these three things together because they are attached. The gardener is attached to the wheelbarrow with their hands and so they're going to accelerate with the wheelbarrow. So this whole mass accelerates together and so it's considered one thing in our analysis. So the forces we want to know about are the total force of gravity, which is force of gravity on the wheel barrow, force of gravity on the soil, plus the force of gravity on the person. We'll want to know the total normal force on the system which consists of the normal force on the wheel and the normal force on the person. There's going to be some friction in the wheel and the person will exert some force on the ground due to the person, and the ground will in turn exert an equal but opposite force on the person. So here's the force on the person due to the ground, and I'm drawing all these forces originating at the center of mass of the system. So this is the force on the person but I draw its origin here in the middle of that soil there. So, of course to find the acceleration of the system, we would need to know the angle of incline of this hill, theta here. But the question doesn't ask about that, it just says examine the forces. So those are the forces we'd want to know and, but to actually find the acceleration we need to know that angle and I think that's the whole story.