Newton second law involving a gallon of water

[kadoma]

Homework Statement

a box filled of water is over at the beginning of a incline plane of 30 degree, it has a mass of 1 kg,from the bottom of the plane to the top is 10m, the gallon is pushed with a force of 10N to the top, and the gallon is leaking 0.01kg per second

what is the final velocity?

Homework Equations

f=ma

The Attempt at a Solution

analyzing this problem each since the force doesnt change, the mass decrease each second so the acceleration increase each second. i really dont know how to solve this problem when involving a gallon of water leaking.

 

[sandy.bridge]

Only when the mass remains constant does Newton's Second Law of motion reduce to
$$\vec{F}=m\vec{a}$$
When dealing with variable mass, use
$$\vec{F}=\frac{d}{dt}(m\vec{v})$$

 

[kadoma]

here is a picture http://imageshack.us/photo/my-images/254/unledxo.png/
i need to find the final velocity

 

[kadoma]

Only when the mass remains constant does Newton's Second Law of motion reduce to
$$\vec{F}=m\vec{a}$$
When dealing with variable mass, use
$$\vec{F}=\frac{d}{dt}(m\vec{v})$$

so it means the mass is constant, it only changes the velocity

 

[sandy.bridge]

No, the mass is not constant. It is changing with time. Also, did you copy the question down fully, and properly?

 

[kadoma]

well if you dont understand my question u can ask me

 

[kadoma]

as far i understand time is changing as well as mass and velocity

 

[Ray Vickson]

Only when the mass remains constant does Newton's Second Law of motion reduce to
$$\vec{F}=m\vec{a}$$
When dealing with variable mass, use
$$\vec{F}=\frac{d}{dt}(m\vec{v})$$

This equation is known to be incorrect in general, although it is true in some cases. Correct classical variable-mass equations of motion were finally well established in the 1990s! Before that, many incorrect results appeared in the published literature. Google 'variable-mass dynamics' for relevant papers.

RGV

 

[kadoma]

so... this is harder now, can u help me?

 

[PeterO]

Homework Statement

a gallon of water is over at the beginning of a incline plane of 30 degree, it has a mass of 1 kg,from the bottom of the plane to the top is 10m, the gallon is pushed with a force of 10N to the top, and the gallon is leaking 0.01kg per second

what is the final velocity?

Homework Equations

f=ma

The Attempt at a Solution

analyzing this problem each since the force doesnt change, the mass decrease each second so the acceleration increase each second. i really dont know how to solve this problem when involving a gallon of water leaking.

A couple of questions:

Is this a gallon of water or a kilgram of water? A litre of water has a mass of 1 kg.
If this is a gallon, is this a US gallon [8 lb] or an imperial gallon [10 lb],

EDIT: I ask about which gallon as I don't know where you are posting from.

 

[sandy.bridge]

This equation is known to be incorrect in general, although it is true in some cases. Correct classical variable-mass equations of motion were finally well established in the 1990s! Before that, many incorrect results appeared in the published literature. Google 'variable-mass dynamics' for relevant papers.

RGV

Interesting to know.. Especially considering this was in my Calculus textbook from January 2009.

 

[kadoma]

A couple of questions:

Is this a gallon of water or a kilgram of water? A litre of water has a mass of 1 kg.
If this is a gallon, is this a US gallon [8 lb] or an imperial gallon [10 lb],

EDIT: I ask about which gallon as I don't know where you are posting from.

actually is not really a gallon of water....is just a box or tank filled with water which leak every second.

 

[Liquidxlax]

A couple of questions:

Is this a gallon of water or a kilgram of water? A litre of water has a mass of 1 kg.
If this is a gallon, is this a US gallon [8 lb] or an imperial gallon [10 lb],

EDIT: I ask about which gallon as I don't know where you are posting from.

i'm pretty sure that the volume isn't important just the change in mass

 

[PeterO]

actually is not really a gallon of water....is just a box or tank filled with water which leak every second.

If the box was not leaking, it would take only about 2 seconds to reach the top, arriving with a velocity of about 10 m/s.

In two seconds, the mass will have reduced from 1.00 kg to 0.98 kg - a very small change, so the final velocity won't be much bigger.
Since data was given to one specific figure only, the answer should be 1 x 10¹ regardless.

 

[kadoma]

i already solved it