Final answer:
The exact mean speed of all vehicles on the turnpike is unknown without knowing the traffic distribution across the lanes. It lies between 64 and 68 mph, but exact calculation requires data on the average number of vehicles per lane.
Step-by-step explanation:
The question concerns the mean speed of all vehicles on the New Jersey Turnpike, given the mean speeds of vehicles in two separate lanes: the "cars only" lanes and the "any vehicle" lanes.
The mean speed of vehicles on the entire turnpike cannot be calculated without additional information, such as the proportion of vehicles in each lane type. If you were to take a simple average of the two provided speeds (68 mph for cars only and 64 mph for any vehicle), it would not account for how many vehicles are in each lane. Therefore, the mean speed of all vehicles on the turnpike is somewhere between 64 and 68 mph, but the exact number depends on the distribution of the traffic across the two types of lanes.
For a precise calculation, we would need testable data, for example, the average number of vehicles passing per day in each lane type. Non-testable hypotheses like the gravitational pull on each vehicle while in motion would not be relevant to finding the mean speed of the vehicles.