To find the resisting force of the brakes, we need to use the equation for kinetic friction:
Ffriction = friction coefficient x normal force
We can calculate the normal force as the weight of the truck, which is equal to its mass times the acceleration due to gravity:
normal force = mass x gravity = 2000 kg x 9.81 m/s^2 = 19,620 N
We can also use the equation for kinetic energy to find the initial kinetic energy of the truck:
kinetic energy = 1/2 x mass x velocity^2 = 1/2 x 2000 kg x (12 m/s)^2 = 144,000 J
When the truck comes to a stop, all of its initial kinetic energy is dissipated by the resisting force of the brakes over a distance of 15 meters. Therefore, we can use the work-energy principle to find the resisting force of the brakes:
work done by resisting force = change in kinetic energy
resisting force x distance = 144,000 J
resisting force = 144,000 J / 15 m = 9,600 N
Thus, the resisting force of the brakes is 9,600 N.