- 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__