Friction

A box with weight W sits on an inclined plane at an angle θ from the horizontal. Drag the red dot on the interactive Figure to change the angle of the plane. Use the sliders on the right to change each of the variables. For the following activity, the following coordinate system will be used, The x-axis is defined parallel to the inclined plane and is positive moving rightward up the plane

The y-axis is defined perpendicular to the inclined plane and is positive toward the top of the page

positive moments produce a counterclockwise rotation

Use the Figure to Observe when Slipping and Tipping Occur

In the interactive Figure below, use the sliders to change the applied force P and its location, the box’s weight W, the angle of the inclined plane θ, and the coefficients of static and kinetic friction

and

. Observe how the magnitude of the friction force F, the normal force N, and the distance of the normal force from the center of the box x, change as a result.

Before any impending motion (i.e., before slipping occurs), increasing the applied force P has what effect on the magnitude of the friction force F?

Select all that apply

A
It increases
B
It decreases
C
It remains the same

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Before any impending motion, why does the friction force F increase as the applied force P increases?

Select all that apply

A
In order for the box to remain in equilibrium
B
To reduce the normal force acting on the box
C
To reduce the coefficient of static friction between the box and inclined plane
D
To counteract the gravitational force acting on the box

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Increasing the applied force P has what effect on the magnitude of the normal force N acting on the box?

Select all that apply

A
It increases it
B
It decreases it
C
It has no effect on it

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Increasing the applied force P on the box has what effect on the location of the normal force x?

Select all that apply

A
It increases x
B
It decreases x
C
It has no effect on x

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Increasing the height at which P acts on the box has what effect on the location of the normal force x?

Select all that apply

A
It increases x
B
It decreases x
C
It has no effect on x

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Increasing the height at which P acts on the box has what effect on the magnitude of the friction force F?

Select all that apply

A
It increases it
B
It decreases it
C
It has no effect on it

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Increasing the weight W of the box has what effect on the location of the normal force x?

Select all that apply

A
It increases x
B
It decreases x
C
It has no effect on x

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Slipping of the box occurs when which of the following conditions is met?

Select all that apply

A
The normal force exceeds the friction force
B
The component of the forces opposing the friction force exceeds the friction force
C
The friction force exceeds the component of the forces opposing it
D
The applied force exceeds the weight of the box

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If P and W remain the same, increasing the angle θ of the inclined plane can induce slipping because,

Select all that apply

A
Because the coefficient of static friction decreases with increasing θ
B
Because the box's center of gravity shifts, reducing friction between the box and plane
C
Because the weight of the box decreases
D
Because increasing θ increases the component of the forces opposing the friction force, eventually exceeding its magnitude

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The maximum static friction force F_max that exists between the inclined plane and box is equal to,

Select all that apply

A
B
C
D
Something else

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Tipping of the box occurs when which of the following conditions is met?

Select all that apply

A
The normal force exceeds the applied force
B
The normal force exceeds the weight of the box
C
The normal force shifts past the edge of the box
D
The friction force exceeds the weight of the box

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Using the above coordinate system, which of the following is the correct equilibrium equation for the box?

Select all that apply

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For the following question, h is the height along the y-axis at which the applied force P acts on the box. If the normal force N is located at the leftmost edge of the box, which of the following is the correct equilibrium equation for the sum of momentsabout that point?

Friction

Use the Figure to Observe when Slipping and Tipping Occur

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