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So if your average speed is 12.5m/s then peak at the bottom will be 15.5m/s and at the top 9.5m/s

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So if your average speed is 12.5m/s then peak at the bottom will be 15.5m/s and at the top 9.5m/s

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change in kinetic energy = change in potential energy

{1/2 m v(bottom)^2 } - {1/2 m v(top)^2 = m g h

where:

m= mass

g = accel of gravity

v( bottom) = velocity at bottom of loop

v(top) = velocity at too of loop

then if we substitute

v(bottom) = v+u

v(top) = v-u

we get:

{1/2 m (v+u)^2 } - {1/2 m (v-u)^2 } = m g h

simplifies to...

2 v u = g h

or

u = gh/2v

then we put in the numbers...

u = 9.81 x 1.81 / (2 x 12.5) = ... ? ... m/s

i didnt even use the sfi equation editor function

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c

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So mass cancels out and you get 0.5 x velocity squared = gravitational acceleration x height

I'll go slowly here

velocity squared is therefore 2x gravitational acceleration x height

so velocity is the square root of (2x gravitational acceleration x height)

gravitational acceleration is 9.81m/s2

height is 1.8m

velocity is the squareroot of (2x9.81x1.8) m/s

squareroot of (36) is 6 m/s

simples!

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In that case I need to draw on the first law of online physics... never disagree with a moderator

c

c

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The embarrassing bit is I think you may be right.

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c

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so at the top it would be 11.8m/s and at the bottom it would be 13.2m/s. So doing the trials at the very bottom will get you the highest speed but check precisely with a speedometer. I consider +/- 0.7m/s quite significant if accurate measurements are to be attempted.

c

Agreed.I calculate the value of u as 0.7m/s

so at the top it would be 11.8m/s and at the bottom it would be 13.2m/s. So doing the trials at the very bottom will get you the highest speed but check precisely with a speedometer. I consider +/- 0.7m/s quite significant if accurate measurements are to be attempted.

The flywheel effect of the motor etc will reduce the difference a little, I didn't bother to calculate that but guess the above figures are a near enough approximation.

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c

The more you think about it the more things you think about that might make some difference between bottom and top of a vertical set up. For example at the bottom it's got the car's weight added to the centripetal forces and at the top the car's weight is subtracted from the centripetal forces so there's more drag at the bottom. The current on his meter and the hot smell from the motor tells us there's plenty of drag.

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Let say, I build the same test rig with the same setup and I test in my yard would I get the same results?

Right now its,

-13C

Barom 1035bm

Dew point -17C

Humidity 70%

Enjoy,

Shad

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c

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I thought this thread was about sharing ideas and progress to establish a method for testing slot cars at speeds in the range 10-15m/s. Assuming the plan is to reach the upper end of that range i.e.15m/s then some collective ideas and knowledge sharing may help? right?Test Rig currently being built to test up to 15m/s across all id, no it won't be a rug racing affair but purpose built .

As we know Scorpius already tested at 10m/s and passed with flying colours :thumbsup:

We all like slot car bones to chew over... especially those that are race speed related...

c

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who said the goalposts have moved

just back from afternoon Sax practice

just back from afternoon Sax practice

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