Whatever the posted speed limit is.
As we know that the duty of highway patrol is to check that someone is not breaking the speed rule at highway. So they are more interested in to know that what is the instantaneous speed of your car because instantaneous speed tell about the speed of a car at any instant. They have no concern with average speed of your car.
Look at the speedometer.
In full speed and chek the speed
This question makes no sense, what do you mean? the speed of the car does not dictate the posted speed limit.
90
Its speed is 55 mph, and if the highway doesn't curve, then its acceleration is zero.
Well you see considering that highway workers work on the highway and if the speed limit was raised, then there's more of a possibility of a car "flying" down the highway and hitting the highway worker
To determine which car exceeded the speed limit of 60 mph, we would need the speeds of each car traveling on the highway. Any car traveling at a speed greater than 60 mph would be considered to have exceeded the speed limit. Without specific speed data for each car, we cannot identify which one was speeding.
If its speed is constant, its acceleration is nil.
Generally, the average car speed is whatever the speed limit is. While some go over and under, others stay right on the speed limit, making it the average.
The main forces acting on a car moving at a constant speed on a level highway in still air are the driving force from the engine propelling the car forward and the opposing forces such as friction between the tires and the road and air resistance. When these forces are balanced, the car will continue to move at a constant speed.
In the sentence "The car accelerated down the highway," the word "accelerated" means that the car increased its speed.