∵气球在空气中,
∴排开空气的体积:v排=v气球=0.5m3,
∴受到空气的浮力:F浮=ρ空气v排g=1.29kg/m3×0.5m3×10N/kg=6.45N;
∵F浮=G球+F,
∴向下的拉力F=F浮-G球=6.45N-0.5N=5.95N.
故答案为:6.45;5.95;竖直向下.
∵气球在空气中,
∴排开空气的体积:v排=v气球=0.5m3,
∴受到空气的浮力:F浮=ρ空气v排g=1.29kg/m3×0.5m3×10N/kg=6.45N;
∵F浮=G球+F,
∴向下的拉力F=F浮-G球=6.45N-0.5N=5.95N.
故答案为:6.45;5.95;竖直向下.