Variables and controls Transitional Reasoning Download PDF

Questions

1. 1.

   A student investigates how the canopy surface area of a parachute affects the descent time of a falling object dropped from a fixed height of 4.0 meters. The student constructs three parachutes of different surface areas using the same plastic sheeting and attaches an identical 50-gram mass to each canopy. However, because larger canopies require more sheet material, the combined mass of the parachute and payload increases with canopy area. Which modification should the student make to properly control for mass so that canopy surface area is the only independent variable affecting descent time?

   • A) Drop the larger parachutes from proportionally higher release points to offset their greater mass.
   • B) Adjust the attached payload mass in each trial so that the total mass of the canopy and payload remains constant.
   • C) Use different types of canopy materials so that every parachute has the same thickness regardless of area.
   • D) Double the drop height for all trials to allow the parachutes more time to reach their terminal velocities.
2. 2.

   A student investigates whether applying a liquid lubricant to a horizontal track decreases the kinetic friction acting on a sliding aluminum slider. The student measures the deceleration of the slider as it moves along the lubricated track from an initial speed of 1.5 m/s. To evaluate whether the lubricant is responsible for any observed decrease in friction, which baseline control trial must the student conduct under identical ambient conditions?

   • A) Release the same slider from rest on an inclined version of the lubricated track to observe its acceleration.
   • B) Test sliders made of different metals at 1.5 m/s on the lubricated track to compare their respective decelerations.
   • C) Measure the deceleration of the same aluminum slider launched at 1.5 m/s across the identical unlubricated track.
   • D) Measure the static friction force required to initiate motion of the aluminum slider on the lubricated track.
3. 3.

   A physics student investigates how the mass of a cart affects its stopping distance on a level track when a uniform braking force is applied. The student records data for four setups: Trial 1 (mass: 200 g, initial speed: 1.2 m/s, braking force: 0.4 N), Trial 2 (mass: 200 g, initial speed: 2.4 m/s, braking force: 0.4 N), Trial 3 (mass: 400 g, initial speed: 2.4 m/s, braking force: 0.8 N), and Trial 4 (mass: 400 g, initial speed: 1.2 m/s, braking force: 0.4 N). Which pair of trials should the student compare to isolate mass as the independent variable?

   • A) Trial 1 and Trial 2
   • B) Trial 2 and Trial 3
   • C) Trial 3 and Trial 4
   • D) Trial 1 and Trial 4
4. 4.

   A student designs an experiment to investigate how the incline angle of a ramp affects the acceleration of a cart. The student releases the same cart from rest at the same starting position on a track adjusted to various angles (10°, 20°, 30°, and 40°) and uses photogates to record the cart's acceleration during each run. Which choice correctly identifies the independent variable, the dependent variable, and a key controlled variable in this investigation?

   • A) Independent variable: acceleration of the cart; Dependent variable: incline angle of the ramp; Controlled variable: release position of the cart
   • B) Independent variable: incline angle of the ramp; Dependent variable: acceleration of the cart; Controlled variable: mass and release position of the cart
   • C) Independent variable: mass of the cart; Dependent variable: incline angle of the ramp; Controlled variable: photogate spacing
   • D) Independent variable: release position of the cart; Dependent variable: acceleration of the cart; Controlled variable: incline angle of the ramp
5. 5.

   A student investigates how the length of a simple pendulum affects its period of oscillation. In the first trial, the student uses a 0.5-meter string with a 50-gram bob released from an angle of 10°. In the second trial, the student uses a 1.0-meter string with a 100-gram bob released from the same 10° angle. Which statement best explains why this experimental setup cannot reliably determine the effect of pendulum length on the period?

   • A) The angle of release was kept constant instead of being tested as the independent variable.
   • B) The oscillation period is a controlled variable that should have been kept identical across both trials.
   • C) The length of the string should have remained fixed while varying only the mass of the bob.
   • D) More than one independent variable was altered simultaneously by changing both the string length and the bob mass.