A lever enables you to lift objects that are too heavy to lift by hand. The leve

Question

A lever enables you to lift objects that are too heavy to lift by hand. The lever pictured here consists of a long board placed on a pivot. To lift the concrete slab on the left end of the board, the person pushes downward on the right end. Using the concept of torque, explain why a lever makes it easier to lift the heavy slab. Hint: In order for board to "swing" clockwise, thereby lifting the slab, how must the torque exerted by the person on the board compare to the torque exerted by the slab on the board? The slab weighs 1000 newton's. The segment of the board to the right of the pivot is 5 times longer than the segment of the board to the left of the pivot. Assuming the board is very light, how hard must the person push down on the right end of board to lift the slab?

Explanation / Answer

A lever is a simple machine. The mechanical advantage is the ratio of the long segment of the board to the short segment

Thetorquerequired to balance a slab must equal the torque applied by the "long" end.
In order to actually lift the slab, a very tiny amount of torque beyond what the slab is generating, must be applied. If not, the system would remain in equilibrium, and no motion would occur.

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if the slab weighs 1000N, a person could lift it by applying 200N at the other end. So the torque on each end is 1000L where L is the length of the board on the slab side and5L is the length on the other end.

1000N(1m) = XN(5m).

X=200N.

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The student is partially right, since the level has more mass on one end, it ends up applying a torque (since it has more weight, and a larger perpendicular distance to apply the force) but that is a symptom of torque rather than the effect of it.

Essentially, the force that you apply downward is multiplied by the ratio of length between your side and the other side of the lever to move something on the other end of it.

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