Question
Question: A body travels 200 cm in the first two seconds and 220 cm in the next four seconds. What will be the...
A body travels 200 cm in the first two seconds and 220 cm in the next four seconds. What will be the velocity at the end of 7th second from the start?
A
10 cms-1
B
20 cms-1
C
15 cms-1
D
5cms-1
Answer
10 cms-1
Explanation
Solution
Using s = ut + 1/2 at2 we get
200 = u(2) + 1/2 a(2)2 ………… (i)
After 4s i.e. for t = 6s, distance covered is 220 + 200 = 420 cm
∴ 420 = u(6) + 1/2 a(6)2 ……… (ii)
Solving (i) and (ii)
a = -15 cm s-2
and u = 115 cm-1
∴ Velocity after 7s = u + at
= 115 – 15 × 7 = 10 cm s-1