Final answer:
The fractional rate of flow at low values of V tends to differ from its constant value during the experiment because of the nature of fluid flow. At low velocities, the flow rate may not be well-established and can be easily influenced by factors such as friction and disturbances in the system.
Step-by-step explanation:
When the fractional rate of flow is at low values of V (velocity), it tends to differ from its constant value during the experiment because of the nature of fluid flow. According to the equation Q = Av, where Q is the flow rate, A is the cross-sectional area of the pipe, and v is the velocity, the flow rate is directly proportional to the velocity. Therefore, if the velocity is low, the flow rate will also be low. However, at low velocities, the flow may not be well-established and can be easily influenced by factors such as friction and disturbances in the system, causing the flow rate to deviate from its constant value.