1. A train overtakes two persons who are walking in the same direction in which the train is running, at the rate of 2 kmph and 4 kmph and passes them completely in 9 and 10 seconds respectively. The length of the train (in metres)
Write Comment
Comments
By: anil on 05 May 2019 01.59 am
Speed of person 1 = 2 kmph
Relative speed of train with respect to person 1 = s - 2 kmph
Time taken by train to cross person 1 = 9 seconds = 9/3600 hours
Speed of person 2 = 4 kmph
Relative speed of train with respect to person 2 = s - 4 kmph
Time taken by train to cross person 2 = 10 seconds = 10/3600 hours
The distance covered is equal to the length of the train.
Since the length of train is constant, the product of speed and time n=must be the same.
$$(s-2) imes frac{9}{3600} = (s-4) imes frac{10}{3600}$$
$$(s-2)(9)=s-4(10)$$
$$9s - 18 = 10s -40$$
$$s - 22 kmph$$
Length of train = $$(s-2) imes frac{9}{3600}$$
= $$20 imes frac{9}{3600}$$
=$$frac{1}{20} kms$$
= $$50 m$$
Hence Option D is the correct answer
Terms And Service:We do not guarantee the accuracy of available data ..We Provide Information On Public Data.. Please consult an expert before using this data for commercial or personal use
Relative speed of train with respect to person 1 = s - 2 kmph
Time taken by train to cross person 1 = 9 seconds = 9/3600 hours
Speed of person 2 = 4 kmph
Relative speed of train with respect to person 2 = s - 4 kmph
Time taken by train to cross person 2 = 10 seconds = 10/3600 hours
The distance covered is equal to the length of the train.
Since the length of train is constant, the product of speed and time n=must be the same.
$$(s-2) imes frac{9}{3600} = (s-4) imes frac{10}{3600}$$
$$(s-2)(9)=s-4(10)$$
$$9s - 18 = 10s -40$$
$$s - 22 kmph$$
Length of train = $$(s-2) imes frac{9}{3600}$$
= $$20 imes frac{9}{3600}$$
=$$frac{1}{20} kms$$
= $$50 m$$
Hence Option D is the correct answer