Answer:
d = 369.38 km
Explanation:
The speed has a x-component and a y-component.
speed,x = 2.07cos(28.8°) = 1.81 km/s
speed,y = 2.07sin(28.8°) = 1.00 km/s
The time the shell flies is determined by the y-component, when it reaches the highest point the speed is 0 due to the gravitational acceleration.
[tex]v_{f}=v_{0} +a * t[/tex]
0 = 1000 - 9.8 * t
9.8 * t = 1000
t = 102.04 s
After reaching the highest point the shell takes the same time to reach the ground where it was fired, so the total time it flies is 102.04* 2 = 204.08 s
Now you can calculate the distance it moves horizontally while it flies (constant speed)
[tex]d = v*t[/tex]
d = 1.81 km/s * 204.08 s (I used the speed in km/s because the answer needs to be in km)
d = 369.38 km