A car traveling at 30m/s runs out of gas while traveling at a 5 degree slope. How far will it coast before starting to roll back down?
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Anonymous
ANSWERS: 2
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If your homework only included these details, the answer is either really simple or your teacher is messing with you... Judging by your last question, it's probably a frictionless road. You need the object weight most importantly. Friction between the tires and the type of road are second and makes things a-lot harder...lucky we're in physics land. Still... x = object(car+driver) weight y1 = 9.8 m/s^2 (the speed an object on earth falls at 90 degree) y2 = possibly 5/90 or 1/18 to change the fall speed It's been a while since I studied physics...
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One way to do this would be to compute the equations of motion in the horizontal and vertical directions (or in vector form, which is the same) and solve them. But there is a tricksier method used by Galileo. A body on an inclined slope acts as if gravity is reduced down the slope. A slope of 5 degrees is like gravity acting *along* the slope with a force of sin(5 degrees) of its normal value - this is its component in the direction of the slope. This gives you a "reduced gravity" of about -0.87 m/s^2 I made it negative to show it acts against the direction of motion of the car, so that positive means up the slope and negative means down the slope. Now you only need the equation: v = u + a t to solve for when the velocity v becomes 0, just before it starts being negative which means movement down the slope. u = initial speed, v = final speed, a = acceleration, t = time.
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