# Isaac physics

When a ship is moving through the water, the resistance to its motion partly comes from making waves. This is called the
"Wave Making Resistance". The other part of the resistance is known as "Frictional Resistance". For one ship, Frictional Resistance is 80 % of the total resistance.
The remainder comes from making waves.
The frictional resistance is F when the ship is at terminal velocity. Write an equation for Fb, the driving force propelling the ship, in terms of Fr. For example, if you think that the driving force is twice as strong as the frictional
resistance, you would write FD = 2Ff.

Can I pls get help bc I don’t understand this at all?

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Original post by iconliving
When a ship is moving through the water, the resistance to its motion partly comes from making waves. This is called the
"Wave Making Resistance". The other part of the resistance is known as "Frictional Resistance". For one ship, Frictional Resistance is 80 % of the total resistance.
The remainder comes from making waves.
The frictional resistance is F when the ship is at terminal velocity. Write an equation for Fb, the driving force propelling the ship, in terms of Fr. For example, if you think that the driving force is twice as strong as the frictional
resistance, you would write FD = 2Ff.

Can I pls get help bc I don’t understand this at all?

It must be something to do with the fact that it is travelling at terminal velocity (forces are balanced) so in some way the sum of the frictional forces is equal to the propelling forces so the resultant force is 0. I know that isnt much help but let me know how you do.
As well as the above, what is the total reisistance in terms of the frictional resistance? Equate that to the driving force as the net force is zero (terminal velocity).
Original post by Astro746
It must be something to do with the fact that it is travelling at terminal velocity (forces are balanced) so in some way the sum of the frictional forces is equal to the propelling forces so the resultant force is 0. I know that isnt much help but let me know how you do.

Still haven’t got it
Original post by mqb2766
As well as the above, what is the total reisistance in terms of the frictional resistance? Equate that to the driving force as the net force is zero (terminal velocity).

I haven’t got it.
Do you have any further advice pls?
Original post by iconliving
I haven’t got it.
Do you have any further advice pls?

What is the given relationship between total and frictional resistance?
Original post by mqb2766
What is the given relationship between total and frictional resistance?

They are equal?
Original post by iconliving
They are equal?

No, the question says something about wave resistance and something about 80 percent?
Original post by mqb2766
What is the given relationship between total and frictional resistance?

I thought the answer would be fd= ff+1/4fd
Original post by mqb2766
No, the question says something about wave resistance and something about 80 percent?

Ohhhh so it’s 80 percent of it
Original post by mqb2766
No, the question says something about wave resistance and something about 80 percent?

I tried
Fd= 80/100 ff that was wrong so what am i missing?
Original post by iconliving
Ohhhh so it’s 80 percent of it

yes, so write the
total friction = k * frictional resistance
and equate to the driving force as they must be equal at terminal velocity. What is k (in its simplest form) here?

Original post by iconliving
I tried
Fd= 80/100 ff that was wrong so what am i missing?
Original post by mqb2766

What is k sorry?
Original post by iconliving
What is k sorry?

The multiplier which relates the two terms. Its obviously related to the 80%
(edited 1 year ago)
Original post by mqb2766
The multiplier which relates the two terms. Its obviously related to the 80%

I did 80/100*ff and it’s not working is it the right multiplier?
Original post by iconliving
I did 80/100*ff and it’s not working is it the right multiplier?

The total must be greater than the frictional force so it cant be 80/100 for two reasons
* 80/100 less than 1
* its not in the simplest form which isaac usually needs
Original post by mqb2766
The total must be greater than the frictional force so it cant be 80/100 for two reasons
* 80/100 less than 1
* its not in the simplest form which isaac usually needs

So what is the multiplier please I’m really confused?
Original post by iconliving
So what is the multiplier please I’m really confused?

Youre close, but you have not written down the relationship clearly.
total = k * friction
k must be > 1 as the total includes a component from waves as well. What does the 4/5 (80/100) represent using a similar equation, and hence k = ...
Original post by mqb2766
Youre close, but you have not written down the relationship clearly.
total = k * friction
k must be > 1 as the total includes a component from waves as well. What does the 4/5 (80/100) represent using a similar equation, and hence k = ...

1.5?
Original post by mqb2766
Youre close, but you have not written down the relationship clearly.
total = k * friction
k must be > 1 as the total includes a component from waves as well. What does the 4/5 (80/100) represent using a similar equation, and hence k = ...

Sorry I have no idea can you tell me the answer and how to get there because otherwise we’ll be here all night 😂