Question

Topic 2
Uniform and Non-unif
2.1
2014
1. A particle moves with constant acceleration along a
straight line starting from rest. The percentage increase in
its displacement during the 4th second compared to that in
the 3rd second is
IWB JEE1
(a) 33% (h) 40% (0)66% (d) 77%
​

Answer 1

a is the acceleration

since the acceleration is constant / uniform

displacement in nth second formula is

Snth = Sn -S(n-1)

or

Snth=u+a/2(2n-1)

S4= S4 - S3

S4=u+7a/2. »»»»»S4=2u+7a

2

S3=u+5a/2 »»»»2u+5a

2

their ratio is

S4/S3=2u+7a

2u+5a

since the block in starting it is at rest

therefore it initial velocity is0.

S4=7a=7 =1.4

S3 5a 5

in% it is 5/7 x100 ~70%