Linear Movement along a direction set by an angle

angular_velocity.lua

Movement = Class{}

function Movement:init(x, y, angle, speed)
    self.position = vector(x, y)
    self.angle = angle
    self.speed = speed
    self.velocity = self.speed * vector(math.cos(self.angle), math.sin(self.angle))
end

function Movement:update(dt)
    self.position = self.position + self.velocity * dt
end

function Movement:getCoords()
    return self.position:unpack()
end 

angular_velocity_2.lua

function love.load()
    x, y = 100,100
    angle = 0
    image = love.graphics.newImage('image.png')
    speed = 50
    rotspeed = 1
end

function love.draw()
    love.graphics.draw(image,x,y,angle)
end

function love.update(dt)
    if love.keyboard.isDown('up') then
        x = x + math.cos(angle) * speed * dt
        y = y + math.sin(angle) * speed * dt
    end
    if love.keyboard.isDown('down') then
        x = x - math.cos(angle) * speed * dt
        y = y - math.sin(angle) * speed * dt
    end
    if love.keyboard.isDown('left') then
        angle = angle - rotspeed * dt
    end
    if love.keyboard.isDown('right') then
        angle = angle + rotspeed * dt
    end  
end