[填空题]
A projectile is launchej4 pwohci3( wa 6v nst55q8sq;u.u2t:9w 7ml8kbp kt + p zdvu(g3fxp*d 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 stay,wimf2atr7cwyw)v-z; ep /l3 5 /ufx(e3zc lws constant in projectile motion, assuming that air resistance is negligible. Thus the horizontal component of velocity 1.0 seconds after launch will be the sa/( i7 )z-pl/xeucf3 wwwy,fcr atlw;5v 2emz3me as the horizontal component of 2 velocity 2.0 seconds after 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} $.
