/diy/ - Do It Yourself

>>600578
That's beauty.

>>600547
The friction force of the weight is very nearly independent of speed.

You can use the reading from the newton meter as you F in:

Work=F*D

>>600533
>Yes but force is zero when car is travelling at constant velocity?

Net Force = (Force from motor) - (Force of friction)

Typically you use Net Force when calculating work, but that's going to be zero for a vehicle traveling at constant speed on a level surface. If you project requires finding a % efficiency just be sleezy and use (Force of motor) for F int he equation. Make note of it in your presentation or paper or whatever.

I slightly less sleazy solution would be to drag a mass behind you. The mass should have an approximately constant drag once you get it moving. You can measure this whit a newton meter. It takes more force to get it moving than it does to keep it moving. The force of drag is material dependent, so your track will have to be all the same material, and you'll have to measure the drag by pulling the weight around on that material with a newton meter.

That would make the math much simper.

>>600520
>So if I wanted to find out the force I would need to find out air resistance, inertia force, friction force, rolling friction force and (gravity)? Then add them up and declare it as F?

It would be a lot easier to find the force using a newton meter.

>>600505
>burning off the fumes wont help?
Not really, it would probably make the problem worse.

>>600510
Make sure you stir it vigorously.

>>600502
>but how would i convert that into an efficiency (%)
This would be very difficult to do.

In physics terms efficiency=Work done/Energy in.
Work = Force * Distance
Work = Current * Voltage * Time
Work = Mass * Gravity * Height
And a whole bunch more that dont really apply.

This is further complicated by friction, You usually dont consider energy lost to friction as work done. When the car is travelling at full speed, all the energy going to the motor is being used to overcome friction [electrical, mechanical, drag]. Therefore, in physics terms no work is being done.

You can 'cheat' and claim those losses as work done, but you're still going to have a hard time figuring out the Force to use in:
W=F*D
It's going to drop as the fuel gets used up. You could take several measurements at different levels of 'charge' and average them. Then do a couple runs and find the average distance traveled over a complete discharge.

>>600497
Polycyclic aromatic hydrocarbons are no joke.

>>600461
>>600489
You might also try /sci/, they're bretty good at this stuff.

>>600482
Because work is a dot product
If the system moves perpendicular to the applied force: no work is done.

>>600461
Ohh yeah, I saw your thred a few days ago.

bretty cool.

I didn't realize you had the added step of splitting H20. That makes things a little more complicated.

The most practical thing I can think of is measuring the output current and voltage of the fuel cell over a full discharge. If you can do calculus: integrate the area under the curve [with Current*Voltage on the Y-axis and time on the X axis].
If you cant do calculous, just take the averge current times the average voltage times the time it takes to use up your stored hydrogen/oxygen.
Energy = Current*Voltage*Time

Its very difficult to measure the efficiency of a vehicle using the physics definition. Because, once you reach top speed, you're not really doing work any more.
F=m*a
W=F*d
If speed is constant a=0 so,
F=0
W=0

That's why cars are rated in miles/gallon [km/liter] and not percentages.

You can assume the motor has ~90-95% efficiency if you want to include that.
Total Efficiency = (Efficiency of Step 1)*(Efficiency of Step 2)*(Eff.... so on

>>600442
i think a picture will clarify things

The force it pulls with while stationary is the same as the force applied while moving. If you let it go, it will keep accelerating until the force of friction equals the force of the motor.

>>600447
You want to start at 0 and measure how much energy is added to the car as motion [this is the useful work]. Therefore, you want to start the time with no energy and determine how much of the energy as sunlight got converted into kinetic energy of motion in the car.

Are you going to actualy do this, or is this just theory?

>>600395
go back to >>>/g/

>>600415
>could i put a string around the tire and attach it to a newtonmeter

just saw this part. It would be better to attach the newton-meter to the back of the car see how hard hard it pulls. This will prevent errors due the the torque from the wheel being applied at different moment arms.

>>598903
maybe start with a kit, and then move up from there?

>>598788
that will probably work, they also make nailguns for mounting things to concrete

>>597896
wew laddy

>>597906

>>597887
maybe paint the rubber cement on an old sheet of plywood and do the shot in your backyard.

>>597871
Dont do this on asphault, you might damage it. Do it on cement/concrete or bare ground.

Can you do it small scale, or does your shot require it to be full size?

>>597873
I was on my phone when i made that post
I was going to do it for you now that I'm home
but this kind anon beat me to it >>597877

>>597870
>diy
Do it yourself.

>>597437

>>597409
shigg

>>597343
This, water should always be directed away from your house. the ground all the way around your house should be sloped away from the house.