CBST CBST Mechanical Reasoning

Question 1

A gear with 20 teeth meshes with a gear with 10 teeth. If the smaller gear rotates at 60 RPM, how fast does the larger gear rotate?

Accepted Answer

30 RPM

Answer

When two gears mesh, their speeds are inversely proportional to their number of teeth, so the larger gear rotates at 60 × (10/20) = 30 RPM.

Question 2

A lever has its fulcrum 2 feet from a 100-pound load. How much force is needed at the other end, 8 feet from the fulcrum, to lift the load?

Accepted Answer

25 pounds

Answer

Using the principle of moments: Force × 8 = 100 × 2, so Force = 200/8 = 25 pounds.

Question 3

Water flows through a pipe that narrows from a 4-inch diameter to a 2-inch diameter. What happens to the water pressure in the narrower section?

Accepted Answer

It decreases

Answer

According to Bernoulli's principle, when fluid velocity increases through a narrower pipe, the pressure decreases.

Question 4

A pulley system uses 3 ropes supporting a load. Ignoring friction, how much force is required to lift a 300-pound object?

Accepted Answer

100 pounds

Answer

A 3-rope pulley system provides a mechanical advantage of 3, so the required effort is 300 ÷ 3 = 100 pounds.

Question 5

Which type of wrench provides the most torque when loosening a very tight bolt?

Accepted Answer

A long-handled wrench

Answer

Torque = force × distance from the pivot, so a longer handle provides greater torque with the same applied force.

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