Turn on thread page Beta
    • Thread Starter
    Offline

    12
    ReputationRep:
    A river is running at 1.5ms^-1. A man who can row at 2.5ms^-1 in still water wishes to cross to the nearest point on the opposite bank of a river which is 200m wide.

    Velocity of the water is 1.5ms^-1 relative to earth. That is clear.

    Why isn't the velocity of the man 2.5ms^-1 relative to earth? This book says its relative to the water. In this situation the water is running, shouldn't the velocity of the man relative be greater than 2.5ms^-1 for him to end up at the nearest point on the opposite side?
    Offline

    19
    ReputationRep:
    (Original post by AlmostNotable)
    A river is running at 1.5ms^-1. A man who can row at 2.5ms^-1 in still water wishes to cross to the nearest point on the opposite bank of a river which is 200m wide.

    Velocity of the water is 1.5ms^-1 relative to earth. That is clear.

    Why isn't the velocity of the man 2.5ms^-1 relative to earth? This book says its relative to the water. In this situation the water is running, shouldn't the velocity of the man relative be greater than 2.5ms^-1 for him to end up at the nearest point on the opposite side?
    You row relative to the water
    you move as far an observer on the ground different to how you row
    • Thread Starter
    Offline

    12
    ReputationRep:
    (Original post by TeeEm)
    You row relative to the water
    you move as far an observer on the ground different to how you row
    So if the river is running at 100ms^-1, the man's velocity would still be 2.5ms^-1 relative to the water?
    Offline

    19
    ReputationRep:
    (Original post by AlmostNotable)
    So if the river is running at 100ms^-1, the man's velocity would still be 2.5ms^-1 relative to the water?
    yes
    this describes his physical speed...
    however what an outside observer sees is different
 
 
 
Reply
Submit reply
Turn on thread page Beta
Updated: February 26, 2016
Poll
Cats or dogs?
Useful resources

Make your revision easier

Maths

Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

Equations

How to use LaTex

Writing equations the easy way

Student revising

Study habits of A* students

Top tips from students who have already aced their exams

Study Planner

Create your own Study Planner

Never miss a deadline again

Polling station sign

Thinking about a maths degree?

Chat with other maths applicants

Can you help? Study help unanswered threads

Groups associated with this forum:

View associated groups

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Write a reply...
Reply
Hide
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.