In which simple machine is the effort applied between the load and the fulcrum?

Analyze the question: We need a machine where the effort sits between the load and the fulcrum. That is the definition of a third-class lever.

Concept: Classes of levers

• First class: Fulcrum in the middle (load – fulcrum – effort). Examples: seesaw, scissors, pliers, claw hammer (when pulling nails, it pivots about the head, but is often classed as first class).
• Second class: Load in the middle (fulcrum – load – effort). Examples: wheelbarrow, nut crackers, bottle opener.
• Third class: Effort in the middle (fulcrum – effort – load). Examples: sugar tongs, forceps, tweezers, fishing rod, the human forearm.

Checking each option:

• A. Claw hammer: The fulcrum is at the head's contact point, the load (nail) is on the claw close to the fulcrum, and the effort is at the handle's end. Load is in the middle, so this is not a third-class lever (it is second class or first class depending on how it is treated).
• B. Nut crackers: The hinge (fulcrum) is at one end, the nut (load) is in the middle, and the effort is at the handles. This is second class.
• C. Pliers: The pivot is in the middle, so this is first class.
• D. Sugar tongs: The hinge (fulcrum) is at one end, the load (sugar) is at the other end, and you squeeze in between. The effort is between the fulcrum and the load. This is third class. ✔
• E. Wheelbarrow: The wheel axle (fulcrum) is at the front, the load is in the middle, and the effort is at the handles. This is second class.

Answer: D. Sugar tongs.

Exam tip: Remember the middle element with "FLE 123":

• Fulcrum in the middle → class 1
• Load in the middle → class 2
• Effort in the middle → class 3

Whatever is in the middle gives the class, and sugar tongs and tweezers are the classic "effort in the middle" examples.