[问答题]
If air resistance is 8mr kif:d;obh;e9ibm+ f* )wb neglected, show (algebraically) u1t1 j7ld.kf othat a ball thrown vertically upwarf7l d1ut. k1jod with a speed $v_0$ will have the same speed, $v_0$, when it comes back down to the starting point.
