Planning an investigation Transitional Reasoning Download PDF

Questions

1. 1.

   A student plans an experiment to test the hypothesis that the electrical resistance of a metallic conductor is inversely proportional to its cross-sectional area. The laboratory provides several cylindrical wires made of the same alloy but with different diameters, a meter stick, a micrometer caliper, a regulated DC power supply, a voltmeter, an ammeter, and connecting leads. Which experimental procedure correctly isolates the independent variable while controlling necessary variables to test this hypothesis?

   • A) Cutting wires of different measured diameters to the same length, measuring the current and potential difference across each at a constant temperature to calculate resistance, and graphing resistance against the reciprocal of cross-sectional area.
   • B) Cutting wires of the same diameter to various measured lengths, measuring current and potential difference across each at a constant temperature, and graphing resistance directly against wire length.
   • C) Selecting wires made of different metal alloys with identical lengths and diameters, measuring current and potential difference across each, and comparing their calculated resistance values.
   • D) Applying several different voltages across a single wire of fixed length and diameter, measuring the corresponding currents, and graphing potential difference against current to determine the slope.
2. 2.

   A student formulates the hypothesis that increasing the length of a simple pendulum increases its period of oscillation. To test this hypothesis experimentally in a physics laboratory, the student is provided with a support stand, light strings of various lengths, identical metal bobs, a protractor, and a digital stopwatch. Which experimental procedure correctly isolates the independent variable and minimizes measurement error?

   • A) Vary both the string length and the mass of the bob simultaneously in each trial, measuring the duration of a single swing with the stopwatch.
   • B) Keep the string length fixed while releasing the bob from significantly different angles between 10° and 60°, measuring the time for twenty oscillations.
   • C) Test different string lengths using different bob masses, releasing the pendulum from a large amplitude each time to make oscillations easier to observe.
   • D) Test various string lengths while keeping the bob mass and a small release angle constant, measuring the total time for twenty oscillations to determine each period.
3. 3.

   A student is planning an experiment to test the hypothesis that increasing an object's mass increases the kinetic friction force acting on it as it slides along a flat track. The student is provided with a wooden block with a hook, a uniform wooden track, a set of stackable masses, and a spring scale. Which experimental plan correctly isolates the independent variable and allows an accurate measurement of the kinetic friction force?

   • A) Slide the block across tracks made of different materials at varying speeds while keeping the mass of the block constant.
   • B) Accelerate the block rapidly across the wooden track using different masses to ensure the scale records the peak pulling force.
   • C) Change the surface area in contact with the track by rotating the block for each trial while increasing the total mass proportionally.
   • D) Add stackable masses to the block across successive trials while pulling it at a constant speed along the same wooden track.