A total of 10^4 kg of water per second flows over a waterfall 25m high!
If half of the power this flow could be converted into electricity, how many 100W light bulbs could be supplied?
This is a classic gravitational potential energy problem where we are asked for electrical power.
The formula for the potential energy of the water is
P=mgh
where
m = 1×10^4 Kg
g=9.8m/s^2
h=25m
the power is simply the amount of energy available in one second or:
P= 2.45 x 10^6 J/s
With 50% efficiency
Power = 1.225 x 10^6 Watts
divide by 100 watts/bulb
12,250 light bulbs
A 500g rubber ball is dropped from a height of 10m and undergoes a perfectly elastic collision with the earth.
(a) What is the Earth’s velocity after the collision, assuming the Earth is at rest just before the collision.
(b) How many years would it take the Earth to move 1.0mm at this speed?
Well, the second assumption in statement (a) is incorrect, but let’s do the math anyway:
(a)First calculate time for ball to drop 10m
s=1/2 g t^2
s=10m
g=9.8 m/s^2 (the accelaration due to gravity)
solve for t
t= sqrt(2s/g) = sqrt (2.04) or about 1.43 seconds
(2)Next calculate velocity of ball at impact = t [...] Continue Reading…
I’m making an encoder and have to add a PIC to transfer the binary result to BCD-to-7 segment encoder. However, i don’t know how to program a PIC.
Try this site:
BCD to 7 segment with a PIC microcontroller
This site also claims to have the code you need as part of a frequency counter project but you need to provide your email:
Scroll down for the links
Pic frequency counter
Two inductors having inductances L1= 5H and L2=2H and are connected in parallel. The mutual inductance M between the two inductors is 1H. Determine the equivalent inductance (in H) for this system.
With mutual inductance the combined inductance is more complicated to calculate
M=1H
1/Ltotal =( L1 + L2 – 2(M)) / (L1L2 – M^2)
1/Ltotal = (7-2) / (10-1)
1/Ltotal = 5/9
Ltotal = 1.8 H
See also this page for future reference
Series and parallel circuits
What is the connection between people putting bricks in their toilets and Archimedes principle?
Archimedes’ principle is better known as the law of buoyancy.
It states:
Something submerged(partially or fully) in water experiences a force that tries to push it up (and out of the water).
The amount of that force is exactly equal to the WEIGHT of the WATER that the object is displacing.
Back to the submerged bricks…
Assuming a brick is 4″ x 2″ x 8″ you can determine the buoyant force on the brick as follows:
(1)Make a box the exact same size as the brick.
(2)Fill it with water
(3)Weigh the water.
Let’s say [...] Continue Reading…
What is the relationship between the ozone layer and greenhouse gases?
The ozone layer and greenhouse gases are not directly related.
The ozone layer is an area in the atmosphere where more ozone (also known as O3) compared to regular oxygen (O2) collects.
The Ozone layer is very good at blocking Ultraviolet light from the Sun from reaching the surface.
Some other byproducts of pollution (such as Nitrous Oxides from car exhaust) do react with the Ozone in this layer and reduce the amount present.
Greenhouse gasses are very good at trapping heat in the atmosphere by preventing Infrared energy (heat) from radiating back [...] Continue Reading…
The primary purpose of diodes is to allow electrical current to flow in only one direction.
The primary purpose for power diodes is as components of power supplies that are used to convert AC (Alternating Current) line voltage (from the wall socket) into DC (Direct Current) to power an electronic device.
Diodes are typically rated based on 2 numbers:
(1)Maximum current they can carry
(2)The maximum reverse voltage they can withstand (also called PIV or Peak Inverse Voltage)
My son absolutely loves cartoons. Cartoon Network and Toon Disney are the home of some of his favorite shows.
So the idea of actually making his own cartoon was too good to be true.
Flip books have a long history in the making of some classic movies like Bambi and Snow White:
The origins of Animation
This is a great activity for a rainy afternoon (yeah, it was pouring outside!) or when you have a few hours with your child and not much to do.
Since I’m not an animator, the idea of drawing dozens of pictures, each slightly different from [...] Continue Reading…
This past week my wife’s washing machine started acting up…making wierd noises everytime the spin cycle started. How is that relevant you ask? Stay with me…
Well after fixing the machine, the repair guy left the old motor behind in a small cardboard box. For the first couple days I leave the heavy box sitting on our enclosed porch just waiting for garbage day.
This weekend I’m home alone with my son and he happens to notice the box when we wander out onto the porch.
“What’s that daddy?”
“A motor.”
“Should we take it apart?”
His eyes lit up like Christmas [...] Continue Reading…
My son is going to school now!
No, I don’t mean preschool or camp or all those other places meant to prepare them…
I mean Kindergarten! The beginning of (hopefully) 16 years of education.
And I’m suprised at how much it is affecting ME.
Maybe it was sitting in those small chairs with all the other parents for the first Parent/Teacher night…
Flashbacks of first grade…being MUCH smaller than adults…looking UP at BIG people…
the row of ABC’s across the front of the room.
The hardest issue has been trust…of the teachers, not my son.
Will they be kind AND understanding AND teach him to love [...] Continue Reading…