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| 1. | i) the distance travelled. (i) 10 m s-1, (ii) 25 mwith a velocity 20 m s-1to rest after penetratingtarget. Calculate thearget.m s2. Calculate : (i) the 14. A space craft flying in a straight course with avelocity of 75 km s1 fires its rocket motorsfor 6.0 s. At the end of this time, its speed is120 km s in the same direction. Find : (i) thespace craft's average acceleration while themotors were firing, (ii) the distance travelled bythe space craft in the first 10 s after the rocketmotors were started, the motors having been inaction for only 6-0 s.Ans. 2000 m s-2 | 
| Answer» s-displacement, u-initial velocity, v-final velocity,a- acceleration, t-timev=u + atv2 = u2 + 2ass=1/2(u+v)ts=ut + 1/2at^2 a)Calculate the average acceleration when the motors were firing:av. acceleration = change in velocity = 120 - 75 = 45m/s = 7.5m/s^2 time 6s 6s therefore the average acceleration = 7.5km/s^2 b)Distance traveled after the rockets were fired:- Find distance traveled during the 6s when the motors were firing:t=6s, v=120 km/s, u=75km/s, a=7.5km/s2s= 1/2(u+v)t = 1/2(120+75)6 =1/2 x 195 x 6 = 585 km-Find distance after the motors are fired:(the next 4 seconds to make it 10 seconds)After the motors are fired, the craft moves with 120km/s speedThat means in 4s = 4 x 120 = 480kmadd the distance traveled in the 10s = (585 + 480)km = 1065kmTherefore the total distance traveled = 1065 km | |