[填空题]
In a ballistic pendulum experiment, projectile 1 resultshz g53jn,u+ o6y(e qch in a maximum heigmbvmq/svi5nf, :ud;+ eqh: 10kmf(viht h of the pendulum equal to 2.6 cm. A second projectile causes the the pendulum t/m v dq+ei mm1f 0uh;ibk,:ns:vq5f( vo swing twice as high, $h_2=5.2\mathrm{cm}$ The second projectile was how many times faster than the first? $v_1$ = $v_2$ ([color=rgba(0, 0, 0, 0.85)]Round to three decimal places)
