Question

multiple choice questions
answer the following multiple choice questions about the reading.

1. according to the passage, which simple machine utilizes a fulcrum to lift heavy objects,

and how does the fulcrums position affect the force needed?
a. pulley; the more pulleys used, the more force is needed.
b. inclined plane; the steeper the plane, the less force is needed.
c. wheel and axle; the larger the wheel, the more force is needed.
d. lever; the closer the fulcrum is to the object, the less force is needed.

1. a construction worker needs to lift a heavy beam to the top of a building. according to

the passage, which combination of simple machines would provide the greatest
mechanical advantage for lifting the beam?
a. a system of multiple pulleys.
b. an inclined plane with a very steep slope.
c. a single pulley system.
d. a lever with the fulcrum far from the beam.

1. based on the passage, how does a screw provide a mechanical advantage?

a. by using a wedge to split materials apart.
b. by acting as an inclined plane wrapped around a cylinder, requiring less force over a longer
distance.
c. by using a lever to turn the screw.
d. by directly lifting objects with its threads.

Explanation:

1. A lever uses a fulcrum. The formula for a lever is \(F_1\times d_1 = F_2\times d_2\) (where \(F\) is force and \(d\) is distance from the fulcrum). If the fulcrum is closer to the object (\(d_2\) is small), then \(F_1\) (the force needed) is less.
2. A system of multiple pulleys (a block - and - tackle) can significantly reduce the force needed to lift an object. The mechanical advantage of a pulley system is equal to the number of ropes supporting the load.
3. A screw is like an inclined plane wrapped around a cylinder. The formula for the mechanical advantage of an inclined plane is \(MA=\frac{l}{h}\) (where \(l\) is the length of the incline and \(h\) is the height). For a screw, the "length" is the circumference of the circle made by the thread and the "height" is the pitch (distance between threads). So, it requires less force over a longer distance.

Answer:

1. D. Lever; the closer the fulcrum is to the object, the less force is needed.
2. A. A system of multiple pulleys.
3. B. By acting as an inclined plane wrapped around a cylinder, requiring less force over a longer distance.