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

Question

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 (A) 5 cm s -1 (B) 10 cm s -1 (C) 15 cm s -1 (D) 20 cm s -1

Tardigrade Admin · Accepted Answer

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

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

$5 c m s^{- 1}$

$10 c m s^{- 1}$

$15 c m s^{- 1}$

$20 c m s^{- 1}$

$200 = u \times 2 - (1/2) a (2)^{2}$
or $u - a = 100$ ...(i)
$200 + 220 = u (2 + 4) - (1/2) (2 + 4)^{2} a$
or $u - 3 a = 70$ ...(ii)
Solving Eqs (i) and (ii),
we get $a = 15 c m s^{- 2}$
and $u = 115 c m s^{- 1}$ .
Further, $v = u - a t = 115 - 15 \times 7$
$= 10 c m s^{- 1}$ .

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

5cms−1

10cms−1

15cms−1

20cms−1