Asmall airplane flies 780 miles with an average speed of 260 miles per hour. 1.5 hours after the plane leaves, a boeing 747 leaves from the same point. both planes arrive at the same time; what was the average speed of the 747 ?

520 miles per hour

Explanation:

Let the speed of the Boeing 747 be x miles per hour.

The small airplane covers distance of 780 miles with speed 260 miles per hour.

Also,

After 1.5 hours the Boeing 747 leave the same place and reaches at same time. Both covered distance of 780 miles.

So,

Time taken by Boeing 747 + 1.5 hours = Time taken by small plane.

Also,

Time =  Distance/ speed

So,

780 / x + 1.5 = 780/ 260

Solving for x, we get:

x = 520 miles per hour

d. air pressure decreases as altitude increases.

what experimental evidence led scientists to change from the previous model to this one?

a few of the positive particles aimed at a gold foil seemed to bounce back.

the colors of light emitted from heated atoms had very specific energies.

experiments with water vapor showed that elements combine in specific proportions.

cathode rays were bent in the same way whenever a magnet was brought near them.