[填空题]
Two cannonballs, A and B , are firew (.0znix6ffn d from the groun;c;vb ifwre;ru 7.nxj,d6 f9jd with identical initial speeds, but with, finjv6fjbuexd;r; wc ;.7 9r $ \theta_{\mathrm{A}} $ larger than $ \theta_{\mathrm{B}} $
(a)Which cannonball reaches a higher elevation?
(b) Which stays longer in the air?
(c) Which travels farther? If the angle of a is 40 $^{\circ}$ the angle of b is 30$^{\circ}$
参考答案: 空格1: A
空格2: A
空格3: A
本题详细解析:
(a) Cannonball $\mid \mathrm{A}$ , with the larger angle, will reach a higher elevation. It has a larger initial vertical velocity, and so by Eq. 2-11c, will rise higher before the vertical component of velocity is 0 .
(b) Cannonball A , with the larger angle, will stay in the air longer. It has a larger initial vertical velocity, and so takes more time to decelerate to 0 and start to fall.
(c) The cannonball with a launch angle closest to $45^{\circ}$ will travel the farthest. The range is a maximum for a launch angle of $ 45^{\circ}$ , and decreases for angles either larger or smaller than $45^{\circ}$ .
