# Programming science

• 12-13-2001
Mr. Squirrel
Programming science
Hi. I have a question relating to science, but I need the answer to write a program. So, let's see if you have an answer.

Say we are in a place with very little friction. Now, we take a hill and put a car at the top. We also put a car on a crain, holding it up at the same height as the hilltop.
Without friction, all objects on earth fall at 9.8m/s(squared). Saying we let the car on the hill roll (remember, very little friction), what would be the change in velocity. It would not fall at the same rate. Is there a formula for this?
I am making a roller coaster sim.
• 12-13-2001
iain
searching memory for any traces of A level Physics.......

You need to also take into account the air resistance as it is this that dicates the speed of fall, though the friction generated will also have a minor effect.

the change in its velocity will depend on the mass of the body (ie : the car) and the vertical and horizontal distances,

remember bodies accelerate by 9.8ms every second. There is almost certainly a formula for this - but i cannot think of it at the time as it has been over a year since i was doing a level physics.

dV=(dD)/(dtt-dti)
is one of the only ones i remember

i will have a think and post back any more if i remember...
hth
• 12-13-2001
Trance
Given: Acceleration due to gravity = 9.8 m/s

>>Now, we take a hill and put a car at the top. We also put a car >>on a crain, holding it up at the same height as the hilltop.

I think we need to know how steep the incline is... however, with little friction, the car will be accelerating at 9.8 m/s, eventually if it keeps going on the same incline, it will reach a maximum speed. Unfortunately, even if you give us the angle, I'm still not sure how to find the velocity ;/
• 12-13-2001
iain
sorry - forgot to explain the equation

d = delta and means 'change in'
V = velocity
tt = total time taken
dti = correction for external effects (though i doint remember how to calc them )
• 12-13-2001
SilentStrike
Assuming no friction or air resistance, the the object will accelerate at g*sin(theta), where theta is angle of the incline. Testing this for two extremes, a flat surface (theta = 0, sin(0) = 0, and a vertical surface (no surface at all, theta = 90, sin(theta) = 1), shows that it works in both extreme conditions.
• 12-13-2001
Unregistered
Talk to Newton
use this formula

-1/2t^2+i*t+h=c

where t=time passed
i=initial velocity (if something falling, use 0)
h=initial height
c=current height

This does not include area resistance or friction but it should do.
• 12-14-2001
Nick
As you don't have friction I think you can use

mgh = (1/2)mv^2

At least you will find the change in velocity, if you meant acceleration than just use SilentStrikes formula.
• 12-14-2001
RpiMatty
You are lucky cus i just took a Physics 1 College Exam:)
You can use the kinematic equations all ready posted on this board, but you can also use Conservation of Energy to help you out.
Kenetic energy is equal to 1/2 of the mass time the velocity squared
KE = 1/2 m * v^2;
Potential energy is equal Mass * Gravity (9.8) * Height.
PE = m * g * h
So if you have a car at the top of the track it is not moving but has PE.
Then it rolls down a hill and PE transfers into KE.
So if a car rolls from the top of a hill to a bottom of a dip, the speed can be found from those 2 equations
1/2 * m * v^2 = m * g * h
v = sqrt( 2 * g * h )

Look for a physics book and look up motion with constant acceleration. Conservation of momentum and energy will also help you out.
Im just curious what classes have you taken in physics/ what is your current level of education?