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Topic Question Set

Q 1 :    

Two cars are travelling towards each other at a speed of 20 ms-1 each. When the cars are 300 m apart, both the drivers apply brakes and the cars retard at the rate of 2 ms-2. The distance between them when they come to rest is:                    [2024]

  • 200 m

     

  • 50 m

     

  • 100 m

     

  • 25 m

     

(3)

|u→BA|=40 m/s

|a→BA|=4 m/s2

Applying, (v2=u2+2as)relative

0=(40)2+2(-4)(s)⇒s=200 m

Remaining distance =300-200=100 m

So, when both cars will stop then the distance between them, will be

d=300-200=100 m

 

Q 2 :    

Train A is moving along two parallel rail tracks towards north with speed 72 km/h, and train B is moving towards south with speed 108 km/h.

Velocity of train B with respect to A and velocity of ground with respect to B are (in ms-1)               [2024]

  • −30 and 50

     

  • −50 and −30

     

  • −50 and 30

     

  • 50 and −30

     

(4)

=72×518=20 m/s    =108×518=30 m/s

Velocity of train B with respect to train A

VBA=VB-VA=30-(-20)=50 m/s

[Taking South = +ve, North = -ve]

Ground is at rest, so

VGB=VG-VB

=0-(30)=-30 m/s