One motor car A stands 24m in front of a motorcycle B. Both starts from rest along a straight road in the same direction. If A moves with uniform acceleration of 2 m/sec^2, B runs at a uniform velocity of 11 m/sec how many times will they meet?

Category: QuestionsOne motor car A stands 24m in front of a motorcycle B. Both starts from rest along a straight road in the same direction. If A moves with uniform acceleration of 2 m/sec^2, B runs at a uniform velocity of 11 m/sec how many times will they meet?
Editor">Editor Staff asked 11 months ago

One motor car A stands 24m in front of a motorcycle B. Both starts from rest along a straight road in the same direction. If A moves with uniform acceleration of 2 m/sec^2, B runs at a uniform velocity of 11 m/sec how many times will they meet?
 
(a) 3
 
(b) 2
 
(c) 4
 
(d) 1
 
The question was posed to me in semester exam.
 
Query is from Calculus Application in division Application of Calculus of Mathematics – Class 12
NCERT Solutions for Subject Clas 12 Math Select the correct answer from above options 
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1 Answers
Editor">Editor Staff answered 11 months ago

Correct choice is (b) 2
 
The explanation is: Let P and Q be the initial positions of the motor car and motorcycle B respectively, where PQ = 24m.
 
If possible, let us assume that B overtakes A after point R on the straight road after time t seconds from the start.
 
Then, considering the motion of motor car A, we get
 
PR = 1/2 (2) (t^2) = t^2
 
In this case when B runs at a uniform velocity 11 m/sec, we shall have, QR = 11t.
 
Therefore, in this case, QP + PR = QR gives,
 
Or 24 + t^2 = 11t
 
Or t^2 – 11t + 24 = 0
 
Or (t – 3)(t – 8) = 0
 
Or t = 3 or t = 8
 
Clearly, we are getting two real positive values of t.
 
Therefore, A and B will meet twice during the motion.