Equal armed balance is balanced when 20 washers are on one side, and 10 bolts are on the other. Four bolts are added to one side. How many washers must be added to the next side to maintain balance?

Correct Answer: B

Rationale: An equal-armed balance requires equal torque (weight × distance) on both sides. Initially, 20 washers balance 10 bolts, so one bolt equals two washers in weight (20/10 = 2). Adding four bolts increases that side's weight by four bolts, equivalent to 4 × 2 = 8 washers. To maintain balance, eight washers must be added to the other side, keeping total 'washer-equivalents' equal (20 + 8 = 28 vs. 10 × 2 + 4 × 2 = 28). Other options misalign this ratio, making eight the precise counterbalance.

Correct Answer: A

Rationale: Calcium drives contraction by binding troponin, a thin filament protein. This binding alters troponin's shape, shifting tropomyosin away from actin's myosin-binding sites, exposing them for cross-bridge formation. Acetylcholine triggers the initial nerve signal, not calcium's role. Cross-bridge disengagement follows ATP binding, not calcium's action, and ATP hydrolysis energizes myosin beforehand. Calcium's specific effect on troponin unveils actin sites, enabling the sliding filament mechanism, a pivotal step distinguishing it from nerve initiation or energy cycles in muscle physiology.

Correct Answer: B

Rationale: Semimembranosus and semitendinosus, with biceps femoris, form the hamstrings on the posterior thigh, aiding knee flexion and hip extension. The seminal vesicle is a reproductive organ, the forearm contains arm flexors/extensors, and back muscles (e.g., latissimus dorsi) differ in function and location. The thigh's dorsal placement aligns with hamstring anatomy, distinguishing it from unrelated regions, key for understanding lower limb movement.

Correct Answer: A

Rationale: Deltoid reflects shape triangular, like the Greek delta not location, unlike extensor carpi ulnaris (wrist), rectus abdominus (abdomen), and biceps femoris (thigh's femur). Located on the shoulder, deltoid's name emphasizes form over position, distinguishing it from location-specific terms, useful for anatomical recognition beyond regional cues.

Correct Answer: A

Rationale: The leg (knee-to-ankle) extends straightens via the quadriceps, on the thigh's front, contracting to pull the tibia. Hamstrings flex the knee, gluteals extend the hip, and calf muscles (soleus, gastrocnemius) plantarflex the foot, with tibialis anterior dorsiflexing. Quadriceps' specific leg-extension role distinguishes it, critical for standing or kicking motions.