A helicopter ambulance flew from one hospital to another in a straight line. The pilot had to change speed several times due to the presence of other aircraft. The helicopter flew 20 kilometers in 8 minutes. What was the average speed of the helicopter during the trip?

Explanation:

All the rest of the information is extraneous. The only 2 things you have to know are

d = 20 km

t = 8 minutes = 8/60 hours = 0.13333333

So the speed is s = d/t

s = 20/0.1333333 = 150 km/hour

Note: you have not specified what units the speed is. I suppose you could answer 20/8 = 2.5 km/min

the velocity you are looking for is made up of two parts: horizontally velocity, vh, and its vertical velocity, vv. the actual velocity of the ball will be these two parts added together, and because velocity is a vector then they will need to be added vectorially.  

neglecting air resistance etc etc.,  

the horizontal velocity component will be constant (because there is no accelerating force in the horizontal direction.  

vh = 8 ms-1  

the vertical velocity component has an accelerating force: 'g'.  

using v = u +at where a = g = 9.81 ms-2.  

the vertical component of velocity, vv = 0 + gt = vv =9.81 x 2  

vv = 19.62 ms-1 . the zero appears because the virtical component of velocity at time t=0 is zero. remember, the ball was thrown horizontally.  

how fast it will be moving (it actual path (being a parabola )) will be the vector sum of these two.  

adding vectorally gives: -  

v = sqr root (8^2 + 19.62^2) = sqr root(64+384.9) = 21.18 or 21.2 ms-1

come closer and become far apart and become steam/gas