A body travels 200 cm in the first 2 s and 220 cm in the next 4 s with deceleration. The velocity of the body at the end of the seventh second is

200=u×2−(1/2)a(2)2 or  u−a=100                                          ....(i) 200+220=u(2+4)−(1/2)(2+4)2a or  u−3a=70                                          ....(ii) Solving Eqs (i) and (ii), we get a=15cms−2 and u=115cms−1.  Further, v=u−at=115−15×7=10cms−1