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Two cars are travelling in the same direction with a velocity of 60km/kmhh . They are separated by a distance of 5km. A truck moving in the opposite direction meets the two cars in a time interval of 3min. The velocity of the truck is (inkm/kmhh)​
A. 20
B. 30
C. 40
D. 60

Answer
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Hint: The velocity of a particle is defined as distance covered per unit time taken. When two bodies move in the opposite direction then their velocities add up to calculate the relative velocity and when two bodies are in the same direction then their velocities are subtracted to calculate the relative velocity.

Complete step by step answer:
Given: The velocity of two cars is60km/kmhh. The distance between two cars and a truck is 5km. The time taken by the truck to meet cars is 3min.
The formula to calculate the relative velocity of the truck with respect to cars is vt=dt
Here, vt is the relative velocity of the truck, d is the distance covered and t is the time taken to cover the distance.
Substitute 5km ford and3min for t in the formula to calculate the relative velocity of the truck.
vt=5km(3min)(1h60min)=5km0.05h=100km/kmhh
Since the truck moves in the opposite direction of the cars, thus the formula to calculate the relative velocity of the truck is
vt=v+vc
Here, v is the velocity of a truck and vc is the velocity of a car.
Substitute 100km/kmhh for vt and 60km/kmhh for vc in the formula and solve to calculate the velocity of the truck.
100km/kmhh=v+60km/kmhh
v=100km/kmhh60km/kmhh
=40km/kmhh
Thus, the velocity of truck is 40km/kmhh

So, the correct answer is “Option C”.

Note:
The relative velocity of the system increases when the particles move in the opposite direction but it decreases when the particles move in the same direction.