Newton's 2nd law of motion
Definition
The relationships between an object's mass, acceleration and the amount of force applied.
Formula: F=ma
Guitars
You can play a guitar in a soft and quiet tone or you can play it loud. It all depends on how fast or how hard you push down on the strings.
Bikes
When you want to accelerate on your bike you must pedal faster in order gain more speed.
Skate boarding
In order accelerate the skater must push his or her foot against the ground.
Darts
In order to hit the target you need to throw the dart fast so it can go further.