Home
Class 12
PHYSICS
Two cars are moving in the same directio...

Two cars are moving in the same direction with the same speed `30 km//hr`. They are separated by a distance of `5 km`, the speed of a car moving in the opposite direction of it meets these two cars at an interval of `4` minutes, will be.

A

40 km/hr

B

45 km/hr

C

30 km/hr

D

15 km/hr

Text Solution

Verified by Experts

The correct Answer is:
B
The two car (say A and B) are moving with same velocity, the relative velocity of one (say B) with respect to the other A,
A,`vecv_(BA)=vecv_b-vecv_A=v-v=0`
So the relative separation between them (`=5`km) always remains the same.
Now if the velocity of car (say C) moving in opposite direction to A and B, is `vec_C` relative to ground then the velocity of car C
relative to A and B will be `vec_(rel.)=vec_C-vecv`
But as `vecv` is oppsite to `v_C`
So `v_(rel.)=v_c-(-30)=(v_C+30)(km)/(hr)`.
So, the time taken by it to cross the cars A and B
`t=(d)/(v_(rel.))implies(4)/(60)=(5)/(v_C+30)`
`impliesv_C=45(km)/(hr)`.
Promotional Banner

Similar Questions

Explore conceptually related problems

Two cars are moving is one a same line dimension in opposite direction with the same speed v. The relative velocity of two cars w.r.t. each other is

A car is moving on a straight road covers one third of the distance with a speed of 30 km/h and the rest with a speed of 50 km/h. The average speed of the car is

A car travels a distance of 15 km in 20 minute. Find the speed of the car in ms^(-1)

Two cars A and B are moving in same direction with velocities 30 m/s and 20 m/s. When car A is at a distance d behind the car B, the driver of the car A applies brakes producing uniform retardation of 2m//s^(2) . There will be no collision when :-

A car is moving on a straight road covers one third of the distance with a speed of 20 km/h and the rest with a speed of 60 km/h. The average speed of the car is

A car travels a distance of 15 km in 20 minute. Find the speed of the car in kmh^(-1)

A car is moving in a straight line with speed 18 km h^(-1) . It is stopped in 5 s by applying the brakes. Find the speed of car in m s^(-1) .

Two cars A and B are moving on the straight parallel paths with speeds 36 km h^(-1) and 72 km h^(-1) respectively starting from the same point in the same direction. After 20 min , how much behind is car A and from car B ?

A car travels the first half of a distance between two places a speed of 30 km/hr and the second half of the distance a 50 km/hr. The average speed of the car for the whole journey is

A car travels a distance of 258 km in 3 hours 35 minutes . What is the speed of the car ?