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Composition Setup

Deck of Cards
idbigdeck

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
labelPart A

Part A

What is the magnitude of F?

Solution

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idsysa
System:
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idsysa

Both boxes together as a single .

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idinta
Interactions:
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idinta

External influences from the person (applied force) the earth (gravity) and the floor (normal force).

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idmoda
Model:
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idmoda

.

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idappa
Approach:

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idappa
Card
labelPart 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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idsysb
System:
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idsysb

This time, we will focus only on the front box, which will be treated as a .

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idintb
Interactions:
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idintb

The front box is subject to external influences from the rear box, the earth (gravity) and the floor (normal force).

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idmodb
Model:
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idmodb

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idappb
Approach:

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idappb
Card
labelPart 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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idsysc
System:
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idsysc

The 15 kg box as a .

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idintc
Interactions:
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idintc

The rear box is subject to external influences from the person, the rear box, the earth (gravity) and the floor (normal force).

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idmodc
Model:
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idmodc

.

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idappc
Approach:

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idappc