Question

A car weighing 8200 N is travelling at 130 kph along a 2% grade, assume standard conditions and the following vehicle specific parameters: rolling coefficient = 0.015, drag coefficient = 0.28, and frontal area = 2.3 m^2.

What is the road load due to only rolling resistance?

What is the road load due to only aerodynamic drag?

What is the road load due to only road grade?

How much power is required to maintain speed?

Answer 1

given

mg = 8200 N

v = 130 kph = 36.1111 m/s

tan(theta) = 0.02

theta = 1.145762 deg

uk = 0.015

Cd = 0.28

A = 2.3 m^2

a. load due to rolling resistance , Fr= uk*mg*cos(theta) = 122.9754073775 N

b. load due to aerodynamic drag , Fa= Cd*0.5*rho*v^2*A = 0.28*0.5*1.125*36.111*36.111*2.3 = 472.37556528225 N

c. road load due to grage, Wr = mg*sin(theta) = 163.967089903 N

d. power = F*v

form force balance

F + Fr = Fa + Wr

hence

F = 513.36724780775 N

hence

power = F*v = 18538.2560223 W