CBST CBST Mechanical Reasoning 1 — Questions and Answers
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?
- 30 RPM (Correct answer)
- 60 RPM
- 120 RPM
- 90 RPM
Correct answer: 30 RPM
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?
- 25 pounds (Correct answer)
- 50 pounds
- 100 pounds
- 200 pounds
Correct answer: 25 pounds
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?
- It decreases (Correct answer)
- It increases
- It stays the same
- It reverses direction
Correct answer: It decreases
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?
- 100 pounds (Correct answer)
- 150 pounds
- 300 pounds
- 900 pounds
Correct answer: 100 pounds
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?
- A long-handled wrench (Correct answer)
- A short-handled wrench
- An adjustable wrench
- A box-end wrench
Correct answer: A long-handled wrench
Torque = force × distance from the pivot, so a longer handle provides greater torque with the same applied force.
Question 6: Two balls of equal size but different weights are dropped from the same height in a vacuum. Which hits the ground first?
- They hit at the same time (Correct answer)
- The heavier ball
- The lighter ball
- It depends on their shape
Correct answer: They hit at the same time
In a vacuum, all objects fall at the same rate regardless of mass because gravity accelerates them equally.
CBST CBST Mechanical Reasoning 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?