What is the relationship between force, mass, and motion?

If an object is accelerating, then Force = Mass x Acceleration. If it is moving at a constant speed, then Kinetic Energy = 1/2 mass x velocity squared but in this case, there is no force acting on the object. Perhaps this will help understand the relationship between force and mass. Force is anything that acts on an object, from a person pushing on something to gravity holding the Earth in orbit around the Sun, to cause it to change speed or direction. If there is no change in speed or direction, then no force is acting on it. This relates to mass in the following way. THE GREATER THE MASS, THE GREATER THE FORCE NEEDED TO MAKE THAT MASS CHANGE SPEED OR DIRECTION. Think of it like this; what takes more force to push up a hill, a car, or a bicycle. The bicycle has less mass and therefore requires less force to push it.