Posted by **Harold** on Wednesday, March 4, 2009 at 10:02pm.

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.

- Physics -
**drwls**, Wednesday, March 4, 2009 at 10:20pm
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

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