- #1

Kolika28

- 146

- 28

- Homework Statement
- A solid block, M of mass 1kg, is sliding down a ramp which makes an angle θ=15∘ with the horizontal and has a kinetic coefficient of friction of 0.06. Now assume that you put the ramp and block into a bucket of water so that everything is immersed in water (the block is fully covered). The block is sitting at a height h on the ramp. You can assume the density of water is the same everywhere. Draw the new force diagram and write an equation for the initial acceleration of the block down the ramp. You can ignore friction from the water. The block is made of concrete which has a weight of 2400kg/m3. Assume the water has a weight of 1000kg/m3.

- Relevant Equations
- ##T_b##=weight of water displaced by the block.

So I have made force diagram

And I think that I should find the acceleration by using these equations:

##\sum Fx=w\sin(15)-f_k-T_{x-buoyancy} ##

##\sum F_y=N+T_{y-buouancy}-w ##

I know that the volume of water displaced must be ##V=\frac{1}{2400}m^3## and the mass of the water is then ##m=\frac{1000}{2400}kg##

So ##Tb=\frac{1000}{2400}kg*g##

But the thing that confusses me is that if the block is supposed to slide down the ramp, ∑Fy=0. But then I would have to change the weight of the block, so the new weight would be greater to compensate for the buoyancy force in the y-dircetion. That does not give sense. Does anyone have a clue about these kinds of problems?

And I think that I should find the acceleration by using these equations:

##\sum Fx=w\sin(15)-f_k-T_{x-buoyancy} ##

##\sum F_y=N+T_{y-buouancy}-w ##

I know that the volume of water displaced must be ##V=\frac{1}{2400}m^3## and the mass of the water is then ##m=\frac{1000}{2400}kg##

So ##Tb=\frac{1000}{2400}kg*g##

But the thing that confusses me is that if the block is supposed to slide down the ramp, ∑Fy=0. But then I would have to change the weight of the block, so the new weight would be greater to compensate for the buoyancy force in the y-dircetion. That does not give sense. Does anyone have a clue about these kinds of problems?