Question
A cheetah can catch a deer running with a speed of 54
km/h and is 70 meters ahead of it, in 14 seconds. Find the time taken by the cheetah to catch a zebra that is 160 metres ahead of it and is running with a speed which is 80% of that of the deer.Solution
Speed of the deer = 54 km/h = 54 × (5/18) = 15 m/s Distance covered by the cheetah in 14 seconds = 70 metres + distance covered by the deer in 14 seconds = 70 + 15 × 14 = 70 + 210 = 280 metres So, speed of the cheetah = 280/14 = 20 m/s Speed of the zebra = 15 × (80/100) = 12 m/s So, relative speed of the cheetah with respect to the zebra = 20 – 12 = 8 m/s Hence, time taken by the cheetah to catch the zebra = 160/8 = 20 seconds
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