Parallel Forces on an Incline
  Determine the relationship between angle of inclination and the force needed to keep cart from rolling.
Materials: board, protractor, cart, balance

1.  Sketch the set up with the board at 45o.
2.  Review Pg 124 and note the component of gravity parallel to the incline, the force responsible for the cart rolling down the incline.
Label all the vector components on your sketch.
3.  Set the incline at angles between 0o and 90o as described.  For each angle, record the force in Newtons on the scale. This force prevents the cart from rolling.  Use 10o increments.
4.  Find the mass of the cart and calculate its weight (g = 9.8 m/s2).

1.  Plot a graph of the parallel force (y-axis) as a function of angle θ.  Connect the data points with a smooth curved line.
2.  Now, plot on the same graph the product of (weight of cart)  x (sin θ) at each angle θ.
3.  From the graph, write an equation relating the parallel force, the weight of cart, and sin θ.
4.  Using the graph, estimate by interpolation the approximate angle when the parallel force =  1/2 the weight of the cart. 
Find the sine of this angle and draw a conclusion.
5.  Summary

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