Cast-iron cannonballs used in the War of 1812 were occasionally heated for some extended time, so that when fired at houses and ships, they would set them on fire. If one of these cannonballs with a 20 cm diameter were at a uniform temperature of 1100 K, what heat flux value would exist if it were placed in still air at 300 K? You may assume no thermal radiation effects. Assume air is an ideal gas. Properties of air: k = 52.4 × 10-3W/m∙K, Pr = 0.601, kinematic viscosity ν = 68.1 × 10-6 m2/s. Use the following natural convection correlation for spheres: NuD = 2 + 0.43 RaD1/4

Average heat flux = 10.492 KW/m²

Explanation:

The solved solution is in the attach document.

the minimum constant speed at which she can catch the train is 2.7 m/s

given:

acceleration = 0.6

time = 4.5 s

to find:

velocity = ?

formula used:

from 1st kinematic equation we get,

v = u + at

u = initial speed of train = 0 m/s

v = final speed of the train

a = acceleration of the train

t = time

solution:

from 1st kinematic equation we get,

v = u + at

u = initial speed of train = 0 m/s

v = final speed of the train

a = acceleration of the train

t = time

v = 0 + (0.6 × 4.5)

v = 2.7 m/s

the minimum constant speed at which she can catch the train is 2.7 m/s