Free AFCT Mechanical Comprehension Questions and Answers 1 — Questions and Answers
Question 1: In the gear train shown, Gear 1 turns clockwise. In which direction will Gear 3 turn?
- It will not turn.
- Counter-clockwise.
- Clockwise. (Correct answer)
- The direction is indeterminate.
Correct answer: Clockwise.
When two external gears mesh, they turn in opposite directions. Gear 1 turns clockwise, so Gear 2 (the idler gear) must turn counter-clockwise. Since Gear 2 turns counter-clockwise, Gear 3, which meshes with it, must turn in the opposite direction, which is clockwise.
Question 2: To lift a heavy object with a lever and fulcrum, where should the fulcrum be placed to use the least amount of effort?
- Exactly in the middle of the lever.
- Closer to the person applying the effort.
- Closer to the heavy object. (Correct answer)
- Directly underneath the heavy object.
Correct answer: Closer to the heavy object.
According to the law of the lever, placing the fulcrum closer to the load (the heavy object) increases the mechanical advantage. This means a smaller effort force is required to lift the load because the distance over which the effort is applied is longer than the distance the load is lifted.
Question 3: In a hydraulic lift system, a small amount of force is applied to a small piston. What is the effect on the larger piston?
- A smaller force is exerted over a larger distance.
- An equal force is exerted over an equal distance.
- A larger force is exerted over a smaller distance. (Correct answer)
- An equal force is exerted over a larger distance.
Correct answer: A larger force is exerted over a smaller distance.
This scenario demonstrates Pascal's Principle, which states that pressure applied to an enclosed fluid is transmitted undiminished throughout the fluid. Because pressure equals force divided by area (P=F/A), a small force on a small area creates a certain pressure. This same pressure acting on a larger area on the other piston generates a much larger output force, though it moves a shorter distance.
Question 4: A ball is being swung in a circle on the end of a string. If the string suddenly breaks, in which direction will the ball travel?
- It will continue in a circular path.
- It will fly directly away from the center of the circle.
- It will fly off in a straight line tangent to the circle at the point of release. (Correct answer)
- It will drop straight to the ground.
Correct answer: It will fly off in a straight line tangent to the circle at the point of release.
The string provides the centripetal force needed to keep the ball moving in a circle. When the string breaks, this force disappears. Due to inertia, the ball will continue to travel in the direction it was moving at that instant, which is a straight line tangent to the circular path.
Question 5: Which of the following pulley systems provides the greatest mechanical advantage and makes it easiest to lift the 100lb weight?
- A single fixed pulley attached to the ceiling.
- A single movable pulley attached to the weight.
- Two fixed pulleys and two movable pulleys. (Correct answer)
- A single fixed pulley and a single movable pulley.
Correct answer: Two fixed pulleys and two movable pulleys.
The mechanical advantage of a pulley system is generally equal to the number of rope segments supporting the load. A system with two fixed and two movable pulleys will have four supporting rope segments, providing a 4:1 mechanical advantage, which is greater than the other options and requires the least effort to lift the weight.
Question 6: Two individuals are carrying a heavy, uniform log. Person A is at one end, and Person B is one-quarter of the way from the other end. Who is supporting more of the log's weight?
- Person A.
- They are supporting equal weight.
- The distribution of weight cannot be determined.
- Person B. (Correct answer)
Correct answer: Person B.
This is a problem of levers and moments. The center of gravity of the uniform log is at its midpoint. Person B is closer to the center of gravity than Person A. To balance the moments (weight x distance), the person closer to the center of gravity must support a greater share of the weight.
Free AFCT Mechanical Comprehension Questions and Answers 1
In the gear train shown, Gear 1 turns clockwise.
In which direction will Gear 3 turn?