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ICSE Class 10 Physics Question 6 of 20

Solved 2017 Question Paper ICSE Class 10 Physics — Question 13

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Question 3(c)

An enemy plane is at a distance of 300 km from a radar. In how much time the radar will be able to detect the plane? Take velocity of radio waves as 3 x 108 m s-1. [2]

Answer

Given,

Distance d = 300 km,

Velocity V = 3 x 108 m s-1

If it takes time t for the signal to go up to the enemy plane and come back, then

V=2dt⇒t=2dV=2×(300×103m)3×108ms−1=2×10−3 sV = \dfrac{2d}{t} \\[0.5em] \Rightarrow t = \dfrac{2d}{V} \\[0.5em] = \dfrac{2 \times (300 \times 10^3 m)}{3 \times 10^8 m s ^{-1}} \\[0.5em] = 2 \times 10^{-3} \text{ s}

Hence, the radar will detect the enemy plane in 2 x 10-3 s