Question

show that two objects stay at constant distance apart if both move with same velocity in the same direction.Also prove when two trains move in the opposite directions , the one train appears to move faster ​

Answer 1

Answer:

Relative” means “in comparison to”. Thus, the concept of relative speed is used when two or more bodies moving with some speeds are considered. To make things simpler, one body can be made stationary (i.e. Speed =zero) and take the speed of the other body with respect to the stationary body, which is the sum of the speeds if the bodies are moving in the opposite direction and the difference if they are moving in the same direction. This speed of the moving body with respect to the stationary body is called the relative Speed.

Relative Speed of 2 bodies = Sum of their individual speeds if they are moving in the opposite direction = Difference of their individual speeds if they are moving in the same direction.

Consider A and B starting at the same time, travelling in the opposite direction with a speed of 20 kmph and 30 kmph and they have to travel a distance of 200 km. Now the concept of relative speed can be used to find the time of their meeting.

Two bodies moving towards each other are A and B with speeds 20 kmph and 30 kmph. Now make body A stationary and take the speed of B in reference to A, so relative Speed of B = sum of their respective speeds = 20 + 30 = 50 kmph ( as they are travelling in opposite directions).

Now A can be assumed to be stationary and the total distance has to be travelled by B which he will do with a Speed = 50 kmph. So he will meet A after 200/50 = 4 hrs.