Newton's 2nd law of motion
The relationships between an object's mass, acceleration and the amount of force applied.
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.
When you want to accelerate on your bike you must pedal faster in order gain more speed.
In order accelerate the skater must push his or her foot against the ground.
In order to hit the target you need to throw the dart fast so it can go further.