Motion in a Straight Line
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Question : 8
Total: 27
On a two-lane road, car A is travelling with a speed of 36 km h– 1 – 1
Solution:
Velocity of car A = 36 k m h − 1 = 10 m s − 1
Velocity of carB C = 54 k m h − 1 = 15 m s − 1
Relative velocity ofB A = 15 − 10 = 5 m s − 1
Relative velocity ofC A = 15 + 10 = 25 m s − 1
A s , A B = A C = 1 k m = 1000 m
Time available toB C A =
= 40 s
If car B accelerates with acceleration a, to cross A before car C does, then
u = 5 m s − 1 ,
t = 40 s ,
S = 1000 m ,
a = ?
Using,S = u t +
a t 2 ,
we have,1000 = 5 × 40 +
a × 40 2
or 1000 − 200 = 800 a
ora = 1 m s − 2
Velocity of car
Relative velocity of
Relative velocity of
Time available to
If car B accelerates with acceleration a, to cross A before car C does, then
Using,
we have,
or
or
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