[填空题]
A projectile is launchedc5njrqo/nwu8b,fa1r /s+by,7 mzn , n 5oy;nsai,h,4un8odh y8iqh8 at an angle of $30^{\circ}$ to the horizontal with a speed of $ 30 \mathrm{~m} / \mathrm{s}$. How does the horizontal component of its velocity 1.0 s after launch compare with its horizontal component of velocity 2.0 s after launch?
参考答案: 26±2%
本题详细解析: The horizontal component of the velocity stays co gft 531zxfvv/m.cld:nstant in projectile motion, assuming that air resistance is negligible. Thus the horizontal component of velocity 1.0 seconds after launch will be the same as the horizontal component of 2 velocity 2.0 seconds atv flz 1m.xg/c35d:vffter launch. In both cases the horizontal velocity will be given by $ v_{x}=v_{0} \cos \theta=(30 \mathrm{~m} / \mathrm{s})\left(\cos 30^{\circ}\right)=26 \mathrm{~m} / \mathrm{s} $.
