# Incline Friction Lab - L Friction Incline F10

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```					                                    Inclined Plane – Force of Static Friction
Purpose      This activity will determine the maximum force of static friction acting on a stationary object on an inclined surface at
various angles.

Hypothesis   The force of friction always acts in the opposite direction of the motion that the object would have had if the surface
was frictionless. Friction always acts parallel to the surface of contact but may act in any direction along that contact
surface.

For an object in motion, the force of kinetic friction will act in the opposite direction of the motion. So an object sliding
down a ramp will slow down due to the force of friction acting up the ramp. For an object at rest, the force of static
friction acts in the opposite direction of the net force before friction is added.

Fnet = Fg + Fapplied + Ff

F               > Fapplied ( uphill )     F                                       F
If g ( downhill )                       then f will act uphill, helping the smaller applied and reducing the net force Fnet . At the
maximum force of static friction, the net force is zero, Fnet = 0 , so:

Fg ( downhill ) + Fapplied ( uphill ) = Ff ( uphill / downhill )

The maximum force of friction is related to the normal force of the two objects acting on each other and the
coefficient of frcition, µ, which is determined by the nature of the two surfaces in contact.

Ff = µ FN = µ Fg ⊥ = µ mg cosθ ,

where m = mass of the object, g = accleration due to gravity (9.81 m/s2) and θ is the angle of the incline relative to
the horizontal. The force of friction should have the same value for the same angle whether it is being pulled uphill or
downhill

Materials    dynamics cart       dynamics track (1m or 2m)                    string                  force sensor     Xplorer GLX datalogger

Procedure    Force Sensor and GLX
Secure the force sensor to the string attached to the inverted cart (not on its wheels)
Connect the force sensor to the GLX and turn the GLX on ( ).

Data Collection
1.    Determine the weight (Fg = mg) of the cart by hanging the cart attached by the string to the force sensor.

2.      Set up the ramp at a relatively small angle (one or two text books higher on one end).
3.      Collect data to precisely measure the angle (horizontal length, vertical height, hypotenuse (bottom of ramp)

4.      Pull uphill on the cart, slowing increasing the tension until the cart moves.
5.      Record the maximum force applied.
6.      Repeat until 3 values are within 10% of each other.

7.      Repeat steps 2-6 for the same incline, except pullling downhill.

8.      As a class, repeat all steps above (2-7) for 2 other angles.
Pairs of groups do the same angles, independently.

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Raw Data

Weight of the cart= ______________ N

Table 1. Raw data for maximum forces applied uphill and downhill before the cart moved.

Incline                                Force Uphill (N)                      Force Uphill (N)
A               Trial 1
length:
Trial 2
height:
ramp:                         Trial 3
angle, θA:
Average

B               Trial 1
length:
Trial 2
height:
ramp:                         Trial 3
angle, θB:
Average

C               Trial 1
length:
Trial 2
height:
ramp:                         Trial 3
angle, θC:
Average

Calculated Data

Table 2: Friction forces downhill and uphill for various inclines (included those of other groups*)

Parallel Forces (N)
Angle, θ         Weight, Fg               Applied Uphill         Friction Downhill        Applied Downhill          Friction Uphill

Conclusions
In general, how do the applied forces uphill and downhill compare?
In general, how do the forces of friction uphill and downhill compare?
How do the applied forces change as the angle is increased?
How do the friction forces change as the angle is increased?
How would you improve this experiment to make it more effective, more accurate, more precise, or more interesting?

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