a bike rider ia riding along the sidewalk and hit a tree etump and falls over, is this scenario an example of Newton's first law?
No, this scenario is not an example of Newton's first law, also known as the law of inertia. Newton's first law states that an object at rest will remain at rest, and an object in motion will keep moving with a constant velocity unless acted upon by an external unbalanced force.
In the given scenario, the bike rider was riding along the sidewalk, which means they were already in motion. When they hit the tree stump, they fell over due to the force from the impact, which caused their motion to change. Therefore, this scenario involves an external unbalanced force (the impact with the tree stump) that caused the change in motion, so it does not align with Newton's first law.