You have always been impressed by the speed of the elevators in the IDS building in Minneapolis.  You wonder about the maximum acceleration for these elevators.  You decide to measure it by using your bathroom scale.  While the elevator is at rest on the ground floor, you get in, put down your scale, and stand on it.  The scale reads 130 lbs.  You continue standing on the scale while the elevator goes up, carefully watching the reading.  During the trip to the 50th floor, the greatest scale reading was 180 lbs

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Static and Kinetic Friction

Kinetic friction comes into existence when there are moving surfaces means in other words we can say that the force which comes into existing between moving surfaces is known as kinetic friction.