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Composition Setup
Deck of Cards
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bigdeck
Excerpt
A person pushes a box of mass 15 kg along a smooth floor by applying a perfectly horizontal force F. In the process, the 15 kg box pushes against another box with a mass of 10 kg and causes it to move.
The boxes accelerate horizontally at a rate of 2.0 m/s2.
Card
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Part A
Part A
What is the magnitude of F?
Solution
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id
sysa
System:
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id
sysa
Both boxes together as a single .
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id
inta
Interactions:
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inta
External influences from the person (applied force) the earth (gravity) and the floor (normal force).
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id
moda
Model:
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moda
.
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appa
Approach:
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appa
Card
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Part B
Part B
What is the force applied on the front (10 kg) box by the rear (15 kg) box?
Solution
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id
sysb
System:
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id
sysb
This time, we will focus only on the front box, which will be treated as a .
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id
intb
Interactions:
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intb
The front box is subject to external influences from the rear box, the earth (gravity) and the floor (normal force).
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id
modb
Model:
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id
modb
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id
appb
Approach:
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appb
Card
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Part C
Part C
Suppose we now consider the rear (15 kg) box as an independent system. How can we reconcile the fact that the force applied by the person to this box is 50 N, but the 15 kg box only accelerates at a rate of 2 m/s2?
Solution
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id
sysc
System:
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id
sysc
The 15 kg box as a .
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id
intc
Interactions:
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id
intc
The rear box is subject to external influences from the person, the rear box, the earth (gravity) and the floor (normal force).