Question

A 1400 kg truck goes up a hilly road at a steady 60 km/h. The force of air resistance on the truck is 400 N. If the truck's engine supplies the enrgy to the drive wheels at a rate of 35 kW, what is the slope angle of the road?

I get 7.1 please help, don't really get it.

Answer 1

What are the units of the 7.1 that you get? degrees?

The 60 km/h speed converted to m/s is 16.667 m/s. As the truck goes along the road, it is performing work against friction at a rate of F*V = 400 N * 16.667 m/s = 6666.7 Watts PLUS work against gravity at a rate of M g sin A*V = 228,900 sin A watts

35,000 = 6667 + 228,900 sin A
sin A = 0.1238
A = 7.1 degrees

I agree with your answer, if it was in degrees