Question

Francine rolled a marble down a ramp and timed how long it took for the marble to reach the bottom of the ramp. After one trial, she doubled the height of the ramp and added a thick layer of wool cloth to the surface of the ramp. She conducted three more trials and after reviewing the data, Francine concluded that the height of the ramp had no effect on the speed of the marble rolling down the slope. Which of the following reasons best describes why her conclusion is unsupported?

A) She did not use enough trials for accurate data.
B) The addition of wool cloth may have affected the marble's speed.
C) She did not measure the marble's speed accurately.
D) The height of the ramp may not have been doubled correctly.

Answer 1

The student's conclusion is unsupported because introducing wool cloth as a surface on the ramp could have changed the speed of the marble, due to increased friction, independent of the ramp's height.

Step-by-step explanation:

The conclusion that the height of the ramp had no effect on the speed of the marble rolling down the slope is unsupported because the addition of wool cloth may have affected the marble's speed. The wool cloth could have introduced friction that was not present in the first trial, which means the increase in height and the introduction of a new surface material are two variables that changed simultaneously. Therefore, any difference in the results between trials cannot exclusively be attributed to the change in ramp height, since the surface material was also altered and could significantly impact the marble's motion.