$W_t=2W_d$
$\to W-W_d=2W_d$
$\to 3W_d=W$
Ta có $W=W_d+W_t=\text{const}$
$\to$ khi $W_d$ đạt $\max$ thì $W_t$ đạt $\min=0$
$W_d$ $\max\to v=v_{\max}$
$\to W=W_{d\max}+0=\dfrac{1}{2}mv_{\max}^2$
Do đó:
$3.\dfrac{1}{2}mv^2=\dfrac{1}{2}mv_{\max}^2$
$\to v_{\max}=\sqrt{3.10^2}=10\sqrt3(cm/s)$