Final answer:
As isobars on a weather map get farther apart, indicating larger distances between areas of equal pressure, the horizontal pressure gradient force decreases because the rate of change in pressure over a distance becomes more gradual.
Step-by-step explanation:
On a weather map, isobars are lines that connect points of equal atmospheric pressure. The spacing between these isobars indicates the rate of change of pressure over a distance, which is also known as the pressure gradient force (PGF). The PGF is a crucial concept in understanding wind patterns and weather systems. When the spacing between isobars increases, meaning they are farther apart, the pressure changes less rapidly over a given distance, indicating a weaker PGF. Conversely, when the isobars are close together, there is a steeper pressure gradient and a stronger PGF, leading to higher wind speeds.
To answer the student's question, as the spacing between isobars gets farther apart, the horizontal pressure gradient force decreases. This is because the PGF is directly related to the rate of change in pressure over a distance, and greater spacing means a more gradual change.