[填空题]
A projectile is launc0a7lk 0(wbxzcicq 1v0cfop 2cq8u 6x :hu shm:t +o)nsif1 4r.aed 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 constant in projectile motionj obdw+u n04 5dh(zbj)81d eet, assuming that air resistance is negligible. Thus the horiz8 dwt0 )od5 j+bjud4bne (hz1eontal component of velocity 1.0 seconds after launch will be the same 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} $.
