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course PHY 241
10/10/20117:15 am
I have a couple of questions regarding gravitational forces on inclines. I know we went over them in class, but I'm still a little foggy on it." "Questions and Assignment (University Physics only):
`q001. For the hotwheels car you observed, what is the force per gram while the car is going up the incline, and while it is going down the incline?
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average speed uphill, 20 cm/s. average speed downhill, 30 cm/s. Assume car weighs 10 grams. Uphill force = 400 grams cm/s^2. Downhill force = 300 grams cm/s^2
@& Force isn't mass * speed or mass * velocity.
You don't connect your results to your observations. I wouldn't expect the average uphill speed to be the lesser, but I can't tell whether this is an error in calculation or in data.*@
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What do you conclude is the frictional force acting on the car, per gram of car mass?
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1%
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What is this result, as a fraction of the gravitational force acting on a gram of mass?
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newton of work per gram
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`q002. For a 4 kg cart on a 7 degree incline, what is the net force acting on the cart, assuming that the frictional force is 10% of the total gravitational force acting on it?
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W = Fdcos(theta). Theta = 277 degrees. Cos(277 degrees) = 0.121869. F = 4kg * 9.8 m/s^2 = 39.2 Joules. 10% 39.2 = 3.92. 39.2 - 3.92 = 35.28 Joules.
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What therefore would be its acceleration when coasting up the incline, and when coasting down the incline?
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@& I don't see where you've used that cosine.
Nor do I see where you have calculated the component of the gravitational force along the incline.
Force isn't measured in Joules.
39.2 Newtons is the weight of the object, but only one component of the weight is in the direction of motion.
You've got everything, just need to put it together.*@
@& I can't tell anything about your experiment. You haven't mentioned your data, nor have you shown how it is connected with your answers.
@& You're on the right track on that last problem.*@
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