SIFT Physics and Simple Machines 3 — Questions and Answers
Question 1: A screw advances 2 mm per rotation. If a screwdriver handle has a radius of 4 cm, what is the mechanical advantage? (Use MA = 2πr / pitch)
- Approximately 126 (Correct answer)
- Approximately 8
- Approximately 50
- Approximately 25
Correct answer: Approximately 126
MA = 2π × 0.04 m / 0.002 m ≈ 125.7, approximately 126.
Question 2: An object moving in a circle at constant speed is experiencing which type of acceleration?
- Centripetal acceleration toward the center (Correct answer)
- Tangential acceleration along the path
- Zero acceleration
- Gravitational acceleration only
Correct answer: Centripetal acceleration toward the center
Even at constant speed, circular motion requires centripetal acceleration directed toward the center to change the direction of velocity.
Question 3: A third-class lever always has a mechanical advantage that is:
- Less than 1 (Correct answer)
- Greater than 1
- Equal to 1
- Equal to 2
Correct answer: Less than 1
In a third-class lever, effort is applied between the fulcrum and load, always resulting in a mechanical advantage less than 1, though range of motion increases.
Question 4: Which law of motion states that for every action there is an equal and opposite reaction?
- Newton's Third Law (Correct answer)
- Newton's First Law
- Newton's Second Law
- Law of Conservation of Energy
Correct answer: Newton's Third Law
Newton's Third Law states that forces always come in equal and opposite action-reaction pairs.
Question 5: The unit of work in the SI system is the:
- Joule (Correct answer)
- Watt
- Newton
- Pascal
Correct answer: Joule
Work is measured in joules (J), where 1 J = 1 N·m, the energy transferred when a 1-newton force moves an object 1 meter.
Question 6: A movable pulley provides a mechanical advantage of 2 because:
- Two rope segments support the load (Correct answer)
- The load is twice the effort
- The rope is twice as long as the height
- The pulley doubles gravity
Correct answer: Two rope segments support the load
A movable pulley has two rope segments pulling upward on the load, so each segment supports half the load, giving MA = 2.
Question 7: If friction is present in a simple machine, its actual mechanical advantage compared to its ideal mechanical advantage is:
- Lower (Correct answer)
- Higher
- Equal
- Unrelated
Correct answer: Lower
Friction wastes energy as heat, requiring more input effort than the ideal frictionless case, so actual MA is always lower than ideal MA.
SIFT Physics and Simple Machines 3
A screw advances 2 mm per rotation.
If a screwdriver handle has a radius of 4 cm, what is the mechanical advantage? (Use MA = 2πr / pitch)