Answer:
Power is 15.41 hp
Work is 39205.18 Btu
Explanation:
The power to overcome the drag force is given by the formula:
P = (1/2)ρ v³ A Cd
where,
P = Power
ρ = Density of air = 0.075 lbm/ft³
v = speed of truck = (65 miles/hr)(1 hr/3600 s)(5280 ft/1 mile) = 95.33 ft/s
A = Area = 30 ft²
Cd = drag coefficient = 0.28
therefore,
P = (1/2)(0.075 lbm/ft³)(95.33 ft/s)³(30 ft²)(0.28)
P = (272926 ft².lbm/s³)(1 lbf/32.2 lbm.ft/s²)
P = (8476 ft. lbf/s)(1 hp/550 ft.lb/s)
P = 15.41 hp
Now, for the work of 1 hour:
Work = W = P x time
W = (15.41 hp)(2544 Btu/h / 1 hp)(1 h)
W = 39205.18 Btu
