Answer:
The speed of the truck must be 9.8 ft/s.
The speed of the truck must be 17 ft/s
Explanation:
First, let´s calculate the distance of the car relative to the intersection at time t = 2 s and t = 6 s:
d(t) = 1.1 t² + t +2
d(2) = 1.1 (2)² + 2 + 2 = 8.40 ft
d(6) = 1.1(6)² + 6 + 2 = 47. 6 ft
The car traveled (47.6 ft - 8.40 ft) 39.2 ft in 4 seconds.
Then, the speed of the truck must be (39.2 ft / 4 s) 9.8 ft/s to cover the same distance as the car in 4 seconds.
Now, let´s find the distance of the car to the intersection at time t = 7 and t = 7.1.
d(7) = 1.1(7)² + 7 + 2 = 62.9 ft
d(7.1) = 1.1(7.1)² + 7.1 + 2 = 64.6 ft
The distance traveled by the car in 0.1 s is ( 64.6 ft - 62.9 ft) 1.7 ft
Then the truck must travel with a velocity of (1.7 ft /0.1s) 17 ft/s to cover that distance in 0.1 s.
If the runner ends where she started, then her total displacement is 
, which means her average velocity will be
The total distance she traversed, however, was 
, which gives her an average speed of
Water may come into contact with very hot rock heated by magma
