Heating up the brake pads of a car due to friction, is an example of conversion of work done against friction into thermal energy.
A moving car has kinetic energy. When the brakes are pressed, they exert friction against the rim of the wheel. The brake pads exert a force of friction on the wheels. The force of friction decelerates the car. As the car continues forward for a certain time based on its initial velocity, work is done against the frictional force. The kinetic energy possessed by the car is spent in doing the work against friction. This work done is converted into heat, which heats up the braking pads.
Thus, heating up the brake pads of a car is an example of conversion of its initial kinetic energy into thermal energy, by doing work against friction.