You are Here: Home >< Physics

Motion Question - Waterfall

Announcements Posted on
Last day to win £100 of Amazon vouchers - don't miss out! Take our quick survey to enter 24-10-2016
1. A stream provides a constantly acceleration of 6 ms^-2. A toy boat is pushed directly against the current and then released from a point 1.2m upstream from a small waterfall. Just before it reaches the waterfall, it is travelling at a speed of 5 m/s.

a) Calculate the initial velocity of the boat
b) Calculate the maximum distance upstream from the waterfall the boat reaches.

I have answered both questions correctly, now the only annoying thing is that when I read part B again, it really confuses me -

If the boat is being released 1.2m upstream from a waterfall, surely the maximum distance upstream would be 1.2m and not the answer that I got which was 2m? How can a boat go anymore upstream when the current will just push it downstream beneath the waterfall?

The maths behind it is relatively easy but the more I read into the question the more frustrated I get! Can someone explain with a diagram perhaps??
2. If the boat is released 1.2m from the edge with an initial velocity $U$, then the boat will move further away from the waterfalls edge until the counterflow of the waterfall stops the motion away, and carries the boat with the current.

3. (Original post by The-Spartan)
If the boat is released 1.2m from the edge with an initial velocity $U$, then the boat will move further away from the waterfalls edge until the counterflow of the waterfall stops the motion away, and carries the boat with the current.

Oh that makes sense.

I don't know why but something in my head just kept telling me that as soon as you stop pushing the boat would instantly go downstream rather than carry on upstream...
4. (Original post by CrazyFool229)
Oh that makes sense.

I don't know why but something in my head just kept telling me that as soon as you stop pushing the boat would instantly go downstream rather than carry on upstream...
Forgetting about the initial velocity always happens at least it will stick now :P

Register

Thanks for posting! You just need to create an account in order to submit the post
1. this can't be left blank
2. this can't be left blank
3. this can't be left blank

6 characters or longer with both numbers and letters is safer

4. this can't be left empty
1. Oops, you need to agree to our Ts&Cs to register

Updated: April 6, 2016
TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Today on TSR

How does exam reform affect you?

From GCSE to A level, it's all changing

Who would you like to thank?

Poll
Study resources

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

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