# Homework Help: Power and Energy

1. Jun 5, 2006

### penza

I have two questions
a)Water flows over a waterfall of height 75m of volume flow rate 6.0ms-1 and then lands in a pool below.
Outline the energy changes that take place

b)It is suggested that installing a turbine of the waterfall could provide a source of electrical energy. Estimate the power that might be available, stating one assumption that you make.
(The denstity of water= 1000 m-3)

2. Jun 5, 2006

### siddharth

Do you have any thoughts/ideas on this problem? You need to show your work to get help.

3. Jun 5, 2006

### penza

for sure i thought about it but i dont know...

4. Jun 5, 2006

### Hootenanny

Staff Emeritus
Would you mind posting what you have done thus far? The guidlines of these forums state clearly that one should show one's work before receiveing assistance.

5. Jun 5, 2006

### penza

actually first i thought what energy transfer and i put 75/6 and but then i thought you just have to explain meaning that it goes from vaporisation to convection

6. Jun 5, 2006

### Hootenanny

Staff Emeritus
What ?? I was thinking more along the lines of potential energy ---> kinetic energy?

7. Jun 5, 2006

### penza

ho yeh so actually the energy changes are from potential energy ---> kinetic energy, so thats actually the answer...
thank you

8. Jun 5, 2006

### Hootenanny

Staff Emeritus
What are your thoughts for question (b)...?

9. Jun 5, 2006

### penza

for question B i thought that because they have to install a turbine, looking that the density of water is 1000 than you have to do 1000/6 which is the flow rate so then to find the estimated power

10. Jun 5, 2006

### Hootenanny

Staff Emeritus
You have just basically rephrased the question there . Here's a hint: Think about mass and the relationship in question (a).

11. Jun 5, 2006

### penza

yeh but what do you to find the power

12. Jun 5, 2006

### Hootenanny

Staff Emeritus
HINT Power is the rate at which energy is transfered;

$$P = \frac{dE}{dt}$$

13. Jun 6, 2006

### penza

ok got it thank you

14. Jun 6, 2006

### Hootenanny

Staff Emeritus