Constructing evidence-based explanations Transitional Reasoning Download PDF

Questions

1. 1.

   A student investigates how liquid depth affects hydrostatic pressure by submerging a pressure sensor to different depths in a tank of water. At depths of 0.10 m, 0.20 m, and 0.30 m, the sensor records hydrostatic pressures of 0.98 kPa, 1.96 kPa, and 2.94 kPa, respectively. Which statement represents the most complete and scientifically sound evidence-based explanation of these findings?

   • A) Hydrostatic pressure increases with depth because the weight of the water column increases, meaning sensor readings will always be positive in any liquid.
   • B) Hydrostatic pressure is directly proportional to depth because doubling the depth from 0.10 m to 0.20 m doubles the pressure from 0.98 kPa to 1.96 kPa, as greater depth places a taller, heavier column of water over a given area.
   • C) Hydrostatic pressure increases nonlinearly with depth because the recorded pressures rise from 0.98 kPa to 2.94 kPa, showing that static fluids accelerate downward as depth increases.
   • D) Hydrostatic pressure increases because deeper water becomes significantly more compressed and dense, which drives the pressure up from 0.98 kPa at 0.10 m to 2.94 kPa at 0.30 m.
2. 2.

   A student investigates whether the mass of a pendulum bob affects its period of oscillation while keeping the string length (1.0 m) and release angle (5°) constant. Timing 10 complete oscillations yields 20.1 s for a 50 g bob, 20.0 s for a 100 g bob, and 20.1 s for a 200 g bob. Which statement represents the most scientifically sound and complete evidence-based explanation of these results?

   • A) The period of oscillation decreases slightly as mass increases because heavier objects naturally experience greater gravitational acceleration toward the equilibrium position.
   • B) The slight variation between 20.0 s and 20.1 s proves that the bob mass directly controls the timing of a pendulum, although human reaction time introduced experimental errors.
   • C) The period of a pendulum is independent of the bob's mass, as shown by the virtually identical durations of 20.1 s, 20.0 s, and 20.1 s across a fourfold mass increase, because the proportional increase in gravitational restoring force is balanced by the bob's greater inertia.
   • D) A pendulum's period depends exclusively on string length and release angle, which guarantees that all trials will always produce perfectly identical numerical timings in any laboratory setting.
3. 3.

   A student investigates how the cross-sectional area of a metallic wire affects its electrical resistance while keeping the material, length (1.0 m), and applied voltage (6.0 V) constant. When wires with cross-sectional areas of 0.2 mm², 0.4 mm², and 0.8 mm² are placed into the circuit, the ammeter records currents of 0.5 A, 1.0 A, and 2.0 A, respectively. Which statement represents the most scientifically sound and complete evidence-based explanation of these results?

   • A) Cross-sectional area does not influence electrical resistance because the electric potential difference remains constant at 6.0 V across all three trials, indicating that charge carriers flow at a constant rate regardless of wire thickness.
   • B) Electrical resistance decreases as the cross-sectional area of the wire increases, because doubling the area from 0.2 mm² to 0.4 mm² and 0.8 mm² doubles the current from 0.5 A to 1.0 A and 2.0 A under a constant 6.0 V, demonstrating through $R = V/I$ that a broader conductor provides more pathways for charge carriers.
   • C) Electrical resistance increases with increasing cross-sectional area, because expanding the area from 0.2 mm² to 0.8 mm² requires a greater measured current of 2.0 A, showing that more electrical energy is consumed to drive electrons through a larger volume of metal.
   • D) Electrical resistance is inversely related to wire thickness because the measured current rises from 0.5 A to 2.0 A, which proves that any increase in electric current automatically signifies lower resistance regardless of circuit voltage.
4. 4.

   A student investigates whether contact surface area affects the magnitude of kinetic friction by pulling an 8.0 N rectangular wooden block across a uniform table at a constant velocity. When sliding on its wide 100 cm² face, the spring balance records a pulling force of 2.4 N, and when sliding on its narrow 25 cm² face, it also records a pulling force of 2.4 N. Which statement represents the most complete and scientifically sound evidence-based explanation of the findings?

   • A) Kinetic friction is independent of contact surface area because pulling the block on both its 100 cm² and 25 cm² faces required an identical force of 2.4 N, demonstrating that friction depends on the normal force rather than the macroscopic contact area.
   • B) Kinetic friction increases with contact area because a 100 cm² surface provides more contact points with the table than a 25 cm² surface, which inherently generates more resistance against sliding.
   • C) Kinetic friction is independent of surface area because the normal force remains 8.0 N in both trials, meaning measuring the pulling force was unnecessary since theoretical models already omit contact area.
   • D) Kinetic friction decreases when the block rests on its 25 cm² face because the greater pressure per unit area allows the block to slide more smoothly across the table surface.
5. 5.

   A student investigates how the number of insulation layers wrapped around identical metal cans affects thermal energy loss. Each can starts with equal volumes of water at 80 °C, and after 15 minutes in a 20 °C room, the water temperature drops by 32 °C with 0 layers, 14 °C with 2 layers, and 7 °C with 4 layers of felt. Which statement represents the most complete and scientifically sound evidence-based explanation for this investigation?

   • A) Felt is an ideal thermal barrier because it completely prevents heat from escaping, ensuring that wrapped containers never lose thermal energy to their surroundings.
   • B) The water temperatures dropped by 32 °C, 14 °C, and 7 °C across the trials, which proves that felt is a useful material to measure in classroom temperature experiments.
   • C) Increasing the number of felt layers reduces the rate of thermal energy transfer because additional layers trap more air to hinder conduction, as shown by the temperature drop decreasing from 32 °C to 7 °C.
   • D) Adding more layers of felt increases thermal energy loss because thicker materials increase the surface area exposed to the surrounding cooler air.