- GauthamBiju
Time Interval is Frame Independent ( In Newtonian Mechanics)
In Newtonian mechanics or when frames are inertial ie they are no accelerating wrt to each other the Time interval between two events are independent of the frame of reference
For Example
A motorboat going downstream overcame a raft at a point A; T=60 min later it turned back and after sometime passed the raft at a distance l=6.0 km from point A. Find the flow velocity assuming the duty of the engine to be constant.[Irodov Q1.1]
Solution
This problem can be easily solved using the the above tip
Consider two frames
Frame of reference moving with the stream velocity
Frame of reference wrt to river bank
In the first frame of reference, the raft is stationary , hence boat will take exactly same time to return to the boat and hence a total time of 2T for its entire motion
In the Second frame of reference, the raft has moved a distance l in the same time 2T( from above tip)
Therefore,
Speed of raft = Flow Velocity = l/2T= 3km/ h