InoLab : Ultrasonic sensor + Motor

const int trigPin = 3;
const int echoPin = 4;
long distance;
long duration;
int motor_A = 5; 
int motor_B = 6; 
void setup()
{
  pinMode(motor_A,OUTPUT);
  pinMode(motor_B,OUTPUT);
  pinMode(2,OUTPUT);
  pinMode(trigPin, OUTPUT); 
  pinMode(echoPin, INPUT);
}

void loop()
{
ultra();
motor();
}

void motor(){
 if(distance<30){
  analogWrite(2,255);
  digitalWrite(motor_A,HIGH);
  digitalWrite(motor_B,LOW);
   
 }
 else{
  analogWrite(2,255);
  digitalWrite(motor_A,HIGH);
  digitalWrite(motor_B,HIGH);
 }
}

void ultra(){
digitalWrite(trigPin, LOW);
delayMicroseconds(2);
digitalWrite(trigPin, HIGH);
delayMicroseconds(10);
digitalWrite(trigPin, LOW);
duration = pulseIn(echoPin, HIGH);
distance= duration*0.034/2;
}