# Motion with changing mass

1. Oct 16, 2011

### athrun200

1. The problem statement, all variables and given/known data
https://www.physicsforums.com/attachment.php?attachmentid=40057&stc=1&d=1318764025"

2. Relevant equations
F=m$\frac{dv}{dt}$-v$\frac{dm}{dt}$

3. The attempt at a solution
It seems part b is trivial. Obviously, the propellsion force is constant. To find F, just subs m=m/2

I am not sure wheather I am right.

https://www.physicsforums.com/attachment.php?attachmentid=40058&stc=1&d=1318764025"

#### Attached Files:

File size:
34.4 KB
Views:
66
• ###### 1.jpg
File size:
17 KB
Views:
81
Last edited by a moderator: Apr 26, 2017
2. Oct 16, 2011

### Spinnor

Why should the propulsion force be constant? As the water level goes down the water pressure at the bottom of the bucket will be lower so the water velocity will be less?

3. Oct 16, 2011

### athrun200

I know the force depends on the ejected speed, but the question state that its speed is constant, that's why I say it is constant and the whole question becomes very esay.