A body is moving with uniform acceleration and it covers 20m in 4th second and 30m in 8th second.
Find (i) the initial velocity, (ii) the acceleration of the body.
Find (i) the initial velocity, (ii) the acceleration of the body.
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Answer:
s
n
=u+a/2(2n−1)
s
2
=12
⇒12=u+a/2(2×2–1)
⇒12=u+3a/2 ………. (1)
s
4
=20
⇒20=u+a/2(2×4–1)
⇒20=u+7a/2 ………. (2)
Subtract equation (1) from (2)
s=4a/2
⇒a=4ms
−2
12=u+3/2×4
⇒u=6ms
−1
Distance covered in the 4 seconds after 5
th
second,
=S
9
–S
5
=u(9)+1/2a(9)
2
–[u(5)+1/2a(5)
2
]
=4u+a/2(81–25)
=4×6+4/2×56=136m.