Answer 1:
Hi Tiago, this is a good question and it is definitely something you will have the opportunity to study if you choose to take physics classes. The basic equations of motion relate different values that can help you predict where an item will be some time after being pushed/pulled/thrown/shot/etc... from its initial starting point.
The three basic values you will need to know about are position, velocity, and acceleration. Position tells you about where something is. Velocity tells you about how fast something is going. Acceleration tells you about how quickly something's velocity is changing. These can be put together in the basic equations of motions as follows:
(1) Position = Initial position + (Velocity x time) + (1/2)(Acceleration x time^{2})
This equation relates all three of the values we just talked about. It basically tells us that the position of something after a given amount of time is equal to its starting position added to its velocity multiplied by time (running 5 miles/hour for 1 hour means you've run 5 miles) added to its one half of the product of acceleration and time squared (acceleration is equal to 0 if your velocity does not change). The last part of the equation that involves acceleration allows us to account for changes in the velocity.
For example, if I, for 50 minutes at 5 miles per hour but during the last 10 minutes of my run, I steadily increase my speed from 5 miles per hour to 10 miles per hour, I will have run further than if I ran at 5 miles per hour for the full hour.
(2) Velocity = Initial velocity + (Acceleration x time)
This equation relates the velocity of something after a given amount of time to the acceleration. It is saying that our velocity after a certain time is equal to our initial velocity plus the rate of change in our velocity multiplied by the amount of time it has been changing for.
So, if I start off running at 5 miles per hour and I have an acceleration of 1 mile per hour, per hour (meaning that every hour my velocity increases by 1 mile per hour), after one hour, my velocity will be 6 miles per hour.
Hopefully with these equations, you can start to understand how we can predict motion by using the relationships between those three important parameter: position, velocity, and acceleration.
