Planning an investigation Transitional Reasoning Practice

Questions

1. 1.

   A student formulates the hypothesis: "The magnetic strength of an electromagnet increases when the number of turns in its coil is increased." To test this hypothesis, the student is provided with an iron bolt, insulated wire, a variable-voltage power supply, an ammeter, and a box of identical steel paper clips. Which experimental procedure should the student follow to conduct a scientifically valid investigation?

   • A) Wrap different numbers of wire turns around the bolt, adjust the power supply in each trial to keep the current reading on the ammeter constant, and record the number of paper clips lifted.
   • B) Wrap different numbers of wire turns around the bolt, maintain a constant output voltage from the power supply across all trials, and count the number of paper clips lifted.
   • C) Keep the number of wire turns on the bolt constant, vary the current using the power supply across several trials, and record the maximum number of paper clips lifted.
   • D) Wrap different numbers of turns using wires of different conductive metals around the bolt, maintain a constant current, and count the number of paper clips lifted.
2. 2.

   A student plans an investigation to determine whether the mass of a pendulum bob affects its period of oscillation. The student has access to strings of various lengths, spherical bobs of identical size but different masses, a protractor, a meter stick, and a digital stopwatch. To ensure a scientifically valid test of this hypothesis, which procedure should the student follow?

   • A) Vary the mass of the bob and the length of the string simultaneously while keeping the initial release angle constant, and record the time for ten complete swings.
   • B) Keep the string length and initial release angle constant, measure the oscillation time using bobs of different masses, and calculate the period for each mass.
   • C) Keep the bob mass constant while testing strings of different lengths at several different release angles, and determine the time required for one full swing.
   • D) Change both the bob mass and the release angle in each trial while keeping the string length constant, and compare the resulting oscillation periods.
3. 3.

   A student plans an experiment to investigate whether the temperature of a rubber ball affects its rebound height when it bounces off a flat surface. The student has several identical rubber balls, a thermometer, a thermal bath, and a meter stick. To conduct a scientifically valid investigation, which procedure should the student follow?

   • A) Drop balls of different materials from different release heights while keeping their temperatures constant, and record the rebound height.
   • B) Drop a single ball at room temperature onto several different floor surfaces from the same height, and compare the resulting rebound heights.
   • C) Drop identical balls conditioned to the same temperature from successively increasing heights onto the same floor, and measure the rebound height for each drop.
   • D) Drop identical balls conditioned to different temperatures from the same initial height onto the same floor, and measure each rebound height.
4. 4.

   A student plans an experiment to investigate whether the contact surface area between an object and a table affects the kinetic friction force acting on the object. The student uses a rectangular wooden block whose faces have distinctly different surface areas but identical surface textures. To conduct a scientifically valid investigation, which experimental procedure should the student follow?

   • A) Vary the total mass of the block on each trial while keeping the contact face and pulling speed constant.
   • B) Slide the block across tables made of different materials while keeping the same face in contact each time.
   • C) Change the contact face and simultaneously add extra weights to the top of the block during each trial.
   • D) Slide the block on different faces while keeping the total mass, table surface, and motion speed constant.

Answers and step-by-step solutions appear after you finish the test.