Question

29.
A particle passes through point A and B which are
90 m apart. It takes 6 s to cover this distance with
uniform acceleration. Velocity of particle when it
passes through B point is 20 m/s. What is particle
velocity at A?
(1) 10 m/s
112130 m/s
(3) 15 m/s
(4) 20 m/s

Answer 1

Answer:

Option (1) - 10 m/s

Explanation:

final velocity (v) = 20 m/s

s= 90 m

t= 6 s

Using v= u+at

v-u= at

t= v-u/a

6= 20-u/a

20-u= 6a

u= 20-6a  ----------(i)

Now, Using s= ut+1/2 at²

90= 6(20-6a) + 1/2*a*6²      [from (i) ]

90= 120-36a + 1/2*a*36

90= 120-36a+18a

90= 120-18a

-18a= 90-120

-18a= -30

a= -30/-18

a= 1.67 m/s²  (approximate value)

Now, we have to find initial velocity (u) at point A.

Using v=u+at,

20= u+1.67*6

20=u+10.02

u=20-10.02

u=9.98 m/s

Therefore, u= 10 m/s (approximately).

Hope it helps!!!