The question is as follows...
A motor vehicle having a mass of 0.8 Tonnes is at rest on a incline of 1 in 8 (sine) when the brakes are released. The vehicle travels 30 m down the incline against a constant frictional resistance to motion of 80 N where it reaches the bottom of the slope.
a) Using the principle of conservation of energy, calculate the velocity of the vehicle at the bottom of the incline.
b) Using an alternative method that does not involve a consideration of energy, calculate the velocity of the vehicle at the bottom of the incline.
c) Discuss the merits of the two methods you have used in parts a) and b) of the question. Justify the use of an energy method for these types of problems.
I have done similar questions in class but am not sure which formula i need to use.