Question

5 A body travels 39 m in first 3 seconds and 105 m in next 5 seconds. What will be the velocity
of the body at the end of 10 seconds?
A) 20 m/s
C) 30 m/s
B) 10 m/s
D) 50 m/s
​

Answer 1

Explanation:

From the defenition of average velocity , Sum of initial & final velocity = 2* distance /time .

If u, v & w are the initial velocity, velocity at 3s and velocity at 7s respectively,

u+v = 2*10/3——————1

v+w = 2*15/4 ——————2

u+w= 2*25/7 ———————3

From 1 & 2,

w-u = 5/6 ——————4

and hence acceleration a = 5/(7*6) = 5/42 units.

From 3&4,

w = 335/84 m/s

Velocity at the 8th s = w + a =( 335 /84 ) + ( 10/84 ) = 345/84.