A 1200 kg vehicle initially travelling at 50. km/h experiences an air resistance of 5000 N and road friction of 2200 N. The wheels deliver a force of 7500 N to the vehicle. What is its acceleration?
The forces on the car are:
-- 7,500 N forward, from the engine
-- 5,000 N backwards, from air resistance
-- 2,200 N backwards, from road friction
The net force on the car is (+7,500 - 5,000 - 2,200) = 300 N forward .
Newton said: Force = (mass) x (acceleration)
Divide each side by (mass) :
Acceleration = (force) / (mass)
Acceleration = (300 N) / (1,200 kg) = 0.25 m/s² forward.
Notice the big red herring at the beginning of the question:
It's nice to know that the vehicle starts out traveling at 50 km/hr,
but in order to answer this question, we honestly don't care !