Answer: v = 793.77 mph
Explanation: Linear speed of a circular movement is calculated by using the formula:
v = ω.r
where
ω is angular velocity
r is radius of the path
Angular velocity is the rate of change of the angular position of an object with respect of time, i.e., is how fast an object changes its angular position with time:

The Earth takes 24 hours to complete a rotation, then angular velocity:

0.262 rad/h
At a location 40° north, radius is 3033.5 miles, so:
v = 0.262*3033.5
v = 793.77
At latitude of 40°north, linear speed is 793.77mph.