Forces problem-solving question

A 1200 kg car accelerates from rest at 2.5 m/s2. Take g = 9.8 N/kg. (a) Calculate the resultant force on the car. [3] (b) Calculate the weight of the car. [2] (c) Explain why the car can accelerate even though its weight is much larger than the resultant force. [3]

(a) F = ma = 1200 x 2.5 = 3000 N. (b) W = mg = 1200 x 9.8 = 11 760 N. (c) Weight acts vertically downward and is balanced by the normal contact force; the 3000 N resultant is horizontal and causes the horizontal acceleration.

Award equation, substitution and values. Explanation requires direction of weight, balancing normal force and horizontal resultant force.

Resultant force uses F = ma. Forces in different directions can be considered separately.