Vpython 错误：'float' object 没有属性'_x'

Question

I am writing a Vpython simulation for projectile motion and keep getting the error ('float' object has no attribute '_x') on this line(ball.vel.y = ball.vel.y + g*dt). I have tried changing the values of ball.vel.y to an integer and changing g to an integer but the same error occurs. Here is the code

from vpython import *
import math

ball=sphere(radius=0.1, color=color.red, pos=vector(0.1,0.1,0),make_trail=True)
floor=box(pos=vector(0,0,0), length=10, height=0.01, width=0.01)
g= vector(0,-9.8 ,0)
ball.vel=vector(10*cos(43),10*sin(43),0)
dt=0.1
t=0.0

while(ball.pos.y>-0.001):
    rate(100)
    t=t+dt
    ball.pos.x = ball.pos.x + ball.vel.x*dt
    ball.vel.y = ball.vel.y + g*dt
    ball.pos.y = ball.pos.y + ball.vel.y*dt

Answer 1

g is a vector, as is g*dt, but ball.vel.y is a scalar, and you can't add a vector to a scalar. It's unfortunate that the error message doesn't just say "You can't add a vector to a scalar". I note that if you reverse the two quantities the error message is a bit more understandable: TypeError: unsupported operand type(s) for +: 'vpython.cyvector.vector' and 'float'