A car of weight W is on an inclined road that rises by 100 m over a distance of 1 km and applies a constant frictional force on the car. While moving uphill on the road at a speed of 10 ms−1, the car needs power P. If it needs power while moving downhill at speed v then value of v is :
20 ms−1
15 ms−1
10 ms−1
5 ms−1
From the question
where = angle made by incline plane with the horizontal
While going up,
the net force on car=
Power=P=
using V=10 m/s
i.e
When going down,
the net force on car=
Power=
On comparing we get