Box2d body leaves trail - libgdx

Question

I am trying to shoot a bullet that is a box2d body with linear impulse applied. Everything is fine except that it appears to leave trails and the movement is not smooth. Here's an image of how it is appearing ..this is one bullet .. but is leaving trail while moving ...
This is a single bullet ..rest are just trails that were not cleared. Here is the render method of screen ,
public void render(float delta) {
Gdx.gl.glClearColor(0, 0, 0, 1);
Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);
frameTime = Math.min(delta, 0.25f);
accumulator += frameTime;
while (accumulator >= TIME_STEP) {
world.step(TIME_STEP, 6, 2);
accumulator -= TIME_STEP;
}
stage.act();
stage.draw();
}
Here's the bullet actor
public class Bullet extends Actor {
Sprite bulltetSprite = new Sprite(new Texture(Gdx.files.internal("bullet1.png")));
float x, y;
Body body;
public Bullet(Body b) {
this.body = b;
}
#Override
public void act(float delta) {
x = body.getPosition().x * Constants.PPM;
y = body.getPosition().y * Constants.PPM;
super.act(delta);
}
#Override
public void draw(Batch batch, float parentAlpha) {
super.draw(batch,parentAlpha);
batch.draw(bulltetSprite, x - Constants.BULLET_WIDTH / 2, y - Constants.BULLET_HEIGHT / 2, Constants.BULLET_WIDTH, Constants.BULLET_HEIGHT);
}
}
What am I missing here, so the bullet with move smoothly ...
Edit: The trails appear even when I am not using sprites and just rendering with Box2dDebugRenderer.
Edit 2 : It appears it has to do with the physics. The density I was using for the bullet was way too low .. after setting the density to higher value it seems to work fine now.