Passage VII

Some students performed 3 studies to measure the average horizontal speed of a baseball along its flight path under different wind conditions.

In each study, a pitching machine, a catcher, and a camera were positioned as shown in Figure 1. A measuring tape was extended just above the imaginary line from the pitching machine to the catcher.

Study 1

When no wind was blowing, the students caused the pitching machine to pitch the baseball at a speed of 36 meters per second (m/sec). While the baseball was in flight, its image was recorded on the film in the camera every 0.1 sec. The resulting photograph showed 5 images of the baseball below an image of the measuring tape (see Figure 2).

For each interval defined by adjacent images of the baseball, the students measured the horizontal distance between the images (using the image of the measuring tape) and then divided the distance by 0.1 sec to determine the average horizontal speed of the baseball (see Table 1).

Study 2

When the wind was blowing from east to west with a speed of 15 m/sec, the students repeated the procedure used in Study 1 (see Table 2).

Study 3

When the wind was blowing from west to east with a speed of 15 m/sec, the students repeated the procedure used in Study 1 (see Table 3).

40. In Studies 2 and 3, it took the baseball 0.51 sec and 0.56 sec, respectively, to travel from the pitching machine to the catcher. If these two studies had been performed when the wind was blowing with a speed of 20 m/sec instead of 15 m/sec, the respective times would probably have been:

Answer and Explanation

Your Answer is

Correct Answer is H

Explanation

Comparing table 2 and table 3, it is found that the average speed in Study 3 is smaller, indicating that the movement direction of baseball in Study 3 is against the wind, while in Study 2 it is downwind.

If the wind speed is increased without changing the wind direction, then the downwind baseball in Study 2 will fly faster, so the time to finally reach the catcher will be less than 0.51 sec;

And then The baseball against the wind in Study 3 will fly slower, so the time to finally reach the catcher will be greater than 0.56 sec