q_avideo9_060210

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20:00:30 What is the meaning of the x intercept of the graph of force vs. slope?

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RESPONSE --> The x intercept of the graph of force vs slope is the slope of the graph.

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20:01:27 ** On this graph the x axis represents slope, the y axis represents acceleration. The x axis point occurs when y = 0, so this point represents a slope for which acceleration is zero. Assuming that 'down the incline' is the positive direction, everywhere to the right of this point the acceleration is positive and everywhere to the left is negative. The x intercept therefore represents the maximum slope for which friction is great enough to prevent the ball from accelerating down the slope. Since friction is resisting the weight component down the incline, the x intercept represents the slope when friction and the weight component tending to accelerate the cart down the slope are exactly in balance, equal and opposite. **

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RESPONSE --> Yes the x intercept is the maxium slope for which friction is great enough to precent eh ball from accelerating fown the slope

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20:02:41 When we obtain a linear relationship between force and acceleration, is it plausible that the constant term in the equation is, within experimental uncertainty, zero?

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RESPONSE --> no it is not

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20:03:09 ** The constant term in the equation will be zero only if the graph passes through the origin. This would imply that any nonzero force will produce a nonzero acceleration, and that for example there is either no friction present or friction has been compensated for in some way. **

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RESPONSE --> Most graphs do not pass through the origin.

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20:05:08 For the force vs. acceleration relationship for the car, why should we expect that the acceleration corresponding to a net force equal to the car's weight is the acceleration of gravity?

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RESPONSE --> Because gravity/force is always acting on the car.

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20:05:33 ** When the car is dropped and allowed to fall freely the net force acting on it is its weight, which is the force exerted on its mass by gravity. So the acceleration will be that of gravity. **

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RESPONSE --> Gravity is pulling it down

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