what is the total time of flight of an object projected vertically upwards with

The rate at which the automobile is moving away from the farmhouse is 27.29 m/h.

Explanation:

As shown in the figure, A denotes the position of farmhouse, B be the location of highway intersection and C be the direction along which automobile is moving.

Consider s be the distance between farmhouse and automobile which is represent by AC, x is the distance between intersection and automobile which is represent by BC and the distance between intersection of highway and automobile is represent by AB.

Applying Pythagoras Theorem to the figure,

(AB)² + (BC)² = (AC)²

Since, AB = 7 miles, BC = x and AC = s.

7² + x² = s²

Differentiating both sides of the above equation with respect to time :

When the automobile is 4 miles past the intersection, i.e.

x = 4 miles and = 55 m/h, then

m/h