Type 9: Relative Speed — Same Direction





Q. Two cars are moving in the same direction at speeds of 80 km/h and 60 km/h. What is their relative speed ?


Formula


For two objects moving in the same direction:


Relative Speed = ∣V1−V2∣ , where V1

Solution



  • Speed of first car: V1 = 80 km/h

  • Speed of second car:= 60 km/h 



Therefore,Relative Speed = ∣80−60∣ = 20 km/h

Ans: 20 km/h


Trick: I. Same Direction → Subtract,  II. Opposite Direction → Add






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PRACTICE SET – Relative Speed


Q1. Two cars are moving in the same direction at speeds of 80 km/h and 60 km/h. What is their relative speed ?
A) 10 km/h  B) 20 km/h  C) 30 km/h  D) 140 km/h


Q2. Two trains are moving in the same direction at 90 km/h and 65 km/h. What is their relative speed ?
A) 25 km/h  B) 35 km/h  C) 155 km/h  D) 15 km/h


Q3. Two buses are moving in the same direction at 75 km/h and 45 km/h. What is their relative speed ?
A) 20 km/h  B) 25 km/h  C) 30 km/h  D) 120 km/h


Q4. Two cyclists are moving in the same direction at 28 km/h and 18 km/h. What is their relative speed ?
A) 8 km/h  B) 10 km/h  C) 12 km/h  D) 46 km/h


Q5. Two cars are moving in the same direction at 100 km/h and 72 km/h. What is their relative speed ?
A) 18 km/h  B) 22 km/h  C) 28 km/h  D) 172 km/h



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