If a car is travelling towards a bridge at a constant speed of 20ms-1. The bridge takes 30s to cross entirely. The car creates a force of 3000N. Calculate the mass of the car when it is on the bridge. a=(v2-v1)/t F=ma I figured that a = 0 due to the fact that the car is travelling at constant speed. If a = 0 then isnt it impossible for the car to create a force of 3000N? I am very confused?