Workshop module 10 - Physics 113, Fall 2000
The first two questions on this module are useful for the exam on Thursday.
Now consider lifting the stone with the following arrangement, consisting of two long levers resting on sturdy pivot points (sometimes called fulcrums). The downward arrows represent the forces applied by the workers.
Other things to consider:
Look carefully at the sketch of the levers and the block. Youll see that the distance between each fulcrum and the end of each lever is not exactly the same as the distance between the fulcrum and the edge of the block. Which distance should be used as the lever arm of the force exerted by the block on the lever, and why?
What might the limitations of a simple lever system be?
Can you determine the force exerted on the lever by the fulcrum?
4. Can you stand on your tiptoes and balance? Can you do it with your toes touching the wall of the room? Try it! Why is this not possible?
5. Consider a ladder of mass M and length L leaning against a wall at some angle q , as shown in the sketch to the right. The bottom of the ladder is rubberized (so there's a lot of friction), but the top is bare aluminum and can be considered frictionless.
Other things to consider:
Suppose someone is standing on the ladder. Which forces on the ladder do you expect to be different, and will they be bigger or smaller? Show explicitly how your equations will be modified.
6. For the same ladder above suppose that the coefficient of static friction between the floor and the ladder is known to be m = 1/2.
Other things to consider:
The coefficient of friction between the ladder and the floor is a constant number. How then do you explain (in words) the fact that the ladder becomes unstable as the angle q is decreased?
Which is more likely to slip when leaned against the wall as in this problem, a tall ladder or a short ladder? Assume that the ladders have the same rubber on the bottom.