A car moving with a speed of 40 km per hour if the car engine generated 7 kilowatt power than the resistance in the path of motion of the car will be
Answers
Answer:
rw = mean wheel effective radius
Ft = Fr + Fg + Fd + Fie
Fr = Tyre rolling resistance ( can be in the form of CrN - simplified and treated as independent of velocity)
Fg = forces due to gradient (depending on slope angle, can be positive of negative)
Fd = aerodynamics drag (as a function of air density, drag coefficient, vehicle cross sectional area, and squared of vehicle velocity)
Fie = equivalent inertial force (during acceleration) - (including linear and rotational inertias, due to vehicle mass and rotating component of gear train and wheels)
So you must determine the acceleration required to reach you designed speed.
And must also include overall transmission efficiency in order to get the right size of the motor.
Just to visualize;
for 1000 kg car and everything else constant;
on flat road, @ 25 km/h requires 1.0 kW power
on 5o gradient climbing, @ 25 km/h requires 6.9 kW power
on flat road, accelerating @ 1.4 m/s2 (i.e. 0 - 25 km/h in 5 sec), requires 10.6 kW power.