physics/projects/projectile/index.js

let t=0;
let vy0=50
let vx0=vy0
let x0=140
let y0=80
let g=9.81

let projectile= function (p){
    let width=800
    let height=300
    let dots=[] // Dots that show the projectile path
    p.end=false;
    
    p.setup = function() {
        c=p.createCanvas(Math.min(window.innerWidth,width), height);
        
        vy0t=p.createElement('span', '');
        katex.render("v_0", vy0t.elt);

        r=p.createElement('span', '');
        katex.render("\\vec{r}(t)", r.elt);
        
        vt=p.createElement('span', '');
        katex.render("v(t)", vt.elt);

        vi=p.createElement('span', '');
        katex.render("\\vec{i}", vi.elt);

        vj=p.createElement('span', '');
        katex.render("\\vec{j}", vj.elt);

        
    };
    
    // See explanations in html
    function xt(t) {
        return x0+vx0*t
    }
    function yt(t) {
        return height - (-1/2 * g * t**2 + vy0 * t + y0)
    }
    function vx(t) {
        return vx0
    }
    function vy(t) {
        return -g * t + vy0
    }

    let draw_vectors=function(x,y,skiparrow=false){
        p.push()

        p.stroke(199, 141, 107)
        draw_arrow(p,x,y,x+vx(t),y-vy(t),vt,c,skiparrow)

        p.stroke(200)
        draw_arrow(p,x0,height-y0,x,y,r,c,skiparrow)


        p.stroke(121, 199, 107)
        draw_arrow(p,app.x0,height-app.y0,app.x0,height-app.y0-50,vj,c,skiparrow,true)

        p.stroke(199,119,107)
        draw_arrow(p,app.x0,height-app.y0,app.x0+50,height-app.y0,vi,c,skiparrow)
        
        p.stroke(181, 107, 199)
        draw_arrow(p,app.x0,height-app.y0,app.x0+app.vx0,height-(app.y0+app.vy0),vy0t,c,skiparrow)

        p.pop()
    }
    
    
    p.draw = function() {
        p.clear()
        let x=xt(t)
        let y=yt(t)
        
        // Draw projectile and path
        p.push()
        p.noStroke()
        p.fill(100)
        dots.forEach((elt)=>{p.ellipse(elt[0],elt[1],5,5);})
        p.fill(0)
        p.ellipse(x,y,20,20);
        p.pop()
               
        // Draw vectors
        draw_vectors(x,y)

        p.push()
        p.stroke(0)
        p.ellipse(app.x0,height-app.y0,8)
        p.pop()
        
        // Check simulation state and update it
        if(t>50 || (height-y0)<y){
            p.end=true
            p.noLoop()
        }

        // Update state
        if(!p.end){
            t+=0.1
            dots.push([x,y])
        }
    };
    
    p.windowResized = function(){
        p.resizeCanvas(Math.min(window.innerWidth,width), height);
    }
};

refresh=function(){
    t=0
    x0=app.x0
    y0=app.y0
    vx0=app.vx0
    vy0=app.vy0
    g=app.g
    p5Load()
}



project_init=function(){
    app = new Vue({
        el: '#app',
        data :{
            x0:x0,
            y0:y0,
            vy0:vy0,
            vx0:vx0,
            g:g
        },
        methods:{
            origin_redraw:function(){p5_instance.draw()}
        }
    })
    p5Load()
    
}