The spread of fire from the ground floor to an upper floor of a building primarily due to heat transfer by

The correct answer is by convection.

In fact, in a fluid (like the air in the room full of fire) the warmer parts of the fluid move upward, replacing the colder parts which go down. For this very same reason, the fire spreads moving toward the upper floors of the bulding.

Answer: it will take   4.36 seconds to reach her average velocity 10.69 miles/hour.explanation:   we have equation of motion ,where s is the displacement, a is the acceleration, u is the initial velocity and t is the time taken.average velocity = displacement/ time taken.average velocity = 10.69 miles/hr = 10.69*1.6*1000/(60*60) = 4.75 m/s4.75 = s/ts = 4. 1we also have acceleration = 2.18 m/s², initial velocity = 0 m/sso it will take   4.36 seconds to reach her average velocity 10.69 miles/hour.