# B Galileo's law of inertia

1. Sep 29, 2016

### parshyaa

How galileo proved his first law of motion ie law of inertia by taking conclusions from rolling ball experiments.

2. Sep 29, 2016

### drvrm

Galileo showed that the prevailing idea of Aristotle about forces being necessary to keep objects in motion was not correct..

Although a force is needed to start an object moving,Galileo showed that, once it is moving, no force is needed to keep it moving except for the force needed to overcome friction.
When friction is absent, a moving object needs no force to keep it moving. It will remain in motion all by itself.

Galileo tested his idea by conducting following experiments .

He rolled balls down inclined planes and observed and recorded the gain in speed as rolling continued.
On downward-sloping planes, the force of gravity increases a ball’s speed.

On an upward slope, the force of gravity decreases a ball’s speed.

While rolling on a level surface, the ball neither rolls with nor against the vertical force of gravity and it neither speeds up nor slows down. The rolling ball maintains a constant speed.
Galileo reasoned that a ball moving horizontally would move forever, if friction were entirely absent .
Such a ball would move all by itself of its own inertia.

3. Sep 29, 2016

### parshyaa

4. Sep 30, 2016

### drvrm

the customary thanks on this forum is just to 'like' a post.

5. Sep 30, 2016

### Staff: Mentor

Replying with a few words of appreciation is equally customary.