If by " rolls down all by itself" you mean that it slowly slides down while traveling in the car, then my advice would be to take the door panel off and check to see if the window came off the the lower clips. If every thing looks sound and or the window is electronicly rolling itself down I don't know what to tell you.
Automatic Car windows can sometimes become trouble for the owner. If your window is rolling down, but refuses to roll up, this is due to a burnt wiring inside the motor. The motor is attached to the driving seat door.
A plastic toy car
You should check the struts.
As a car rolls down a hill, the motion and gravitational potential energy(GPE) will be equal when the kinetic energy is equal to the potential energy.
There are three possible hypotheses:Smaller wheels means car rolls slower.Wheel size makes no difference.Smaller wheels means car rolls faster.Take your pick and then use the data to test your hypothesis.
you have to put your handbrake on and then it wont roll down the hill
Car windows go up and down on a track. It has fallen off of the track.
A way to do that is, do you know a car? A mini car Use a mini car and hits a can. That's the only way that I can think.
I believe you should take off the door entirely. The rear window rolls down and it takes the shape of the door and how it wraps around the rear wheel. Use a screw driver to tilt the windows up until it gets removed.
roll / rolls / rolling The balls roll along a channel The car rolls down the road, hits the bus and bursts into flames. Are we rolling?
Lack of lubrication? worn suspension parts?