WTMA Wheels, Axles, and Rotation 5 — Questions and Answers
Question 1: Three gears are in a row: Gear 1 meshes with Gear 2, and Gear 2 meshes with Gear 3. All three gears have the same number of teeth. If Gear 1 rotates clockwise, which direction does Gear 3 rotate?
- Counterclockwise
- Clockwise (Correct answer)
- It does not rotate
- It alternates
Correct answer: Clockwise
Each meshing gear reverses direction; Gear 1 (CW) → Gear 2 (CCW) → Gear 3 (CW), so Gear 3 rotates clockwise like Gear 1.
Question 2: A winch drum (axle) has a radius of 3 inches and its handle (wheel) has a radius of 18 inches. What is the mechanical advantage?
- 3
- 6 (Correct answer)
- 18
- 54
Correct answer: 6
Mechanical advantage of a wheel-and-axle = wheel radius / axle radius = 18/3 = 6.
Question 3: A conveyor belt runs over two rollers of equal diameter. If the left roller is the drive roller turning clockwise (viewed from the front), the belt's top surface moves:
- To the right (Correct answer)
- To the left
- Upward
- Downward
Correct answer: To the right
A clockwise left drive roller pulls the top of the belt toward the right, moving items on the belt surface to the right.
Question 4: Two wheels of different sizes are connected by an axle (fixed together). A rope is wrapped around the larger wheel and a load hangs from a rope on the smaller axle. When the larger wheel is turned, the load:
- Remains stationary
- Rises with less input force than the load's weight (Correct answer)
- Rises but requires more force than the load's weight
- Descends regardless of direction of turn
Correct answer: Rises with less input force than the load's weight
The large wheel provides mechanical advantage: input force × wheel radius = load × axle radius, so less force is needed than the load's actual weight.
Question 5: A wheel is spinning and the brake is applied to slow it down. The braking force acts at a radius of 10 inches from the center. To achieve the same stopping torque with a brake pad placed only 5 inches from the center, you would need:
- Half the braking force
- The same braking force
- Twice the braking force (Correct answer)
- Four times the braking force
Correct answer: Twice the braking force
Torque = Force × radius; to keep torque constant when radius is halved, force must double: F × 5 = F₀ × 10, so F = 2F₀.
Question 6: A vehicle's odometer measures distance traveled based on wheel rotations. If a driver replaces standard tires (circumference 80 inches) with larger tires (circumference 100 inches), the odometer will:
- Read correctly
- Overestimate the distance traveled
- Underestimate the distance traveled (Correct answer)
- Stop working
Correct answer: Underestimate the distance traveled
Each rotation now covers 100 inches instead of 80, but the odometer still counts rotations as if each were 80 inches, so it reads less distance than actually traveled.
Question 7: A water wheel turns a millstone via a system of wooden gears. The water wheel has 60 teeth and the millstone pinion has 10 teeth. The water wheel turns at 5 RPM. At what speed does the millstone turn?
- 5 RPM
- 10 RPM
- 30 RPM (Correct answer)
- 50 RPM
Correct answer: 30 RPM
Speed ratio = driver teeth / driven teeth = 60/10 = 6; millstone speed = 5 × 6 = 30 RPM.
WTMA Wheels, Axles, and Rotation 5
Three gears are in a row: Gear 1 meshes with Gear 2, and Gear 2 meshes with Gear 3.
All three gears have the same number of teeth.
If Gear 1 rotates clockwise, which direction does Gear 3 rotate?