t=0:0.2:2;
x0=0;y0=0;v0x=10.;v0y=10;g=-10.;
x=x0+v0x*t;y=y0+v0y*t+g*t.^2/2;
vx=v0x+t*0;vy=v0y+g*t;
plot(x,y,'-go','LineWidth',3);
hold on
quiver(x,y,vx,vy,0.3,'b')
grid on
hold off