Isaac Newton and Albert Einstein were two supreme scientific geniuses that revolutionized the concepts of mass and acceleration. Beginning in the late 1600s, according to the University of Virginia, Newton provided humanity with three fundamental laws of motion. The three laws defined mass and acceleration with regards to separate units of space and time. Building off of Newton’s findings -- and the contributions of other scientists -- Einstein came up with the theory of relativity. Einstein's theory stated that, due to modern determinations, space and time were not distinct from one another and that nothing can travel faster than the speed of light.
Newton's first law tackled the concept of inertia. If two objects are at rest in relation to one another, they will remain at rest. Alternatively, an object in motion will remain in motion -- unless acted upon by an exterior force. The second law more directly involves the mass of the object. The acceleration rate of an object at rest will depend upon two things: the net force of the object acting upon the resting object and the mass of both objects. Newton's third law stated that with every action, an equal reaction will result. A crow flapping its wings pushes into the air, for example, while the air, simultaneously, pushes back into the wings.
When one object acts upon another, the mass of each object will determine its rate of acceleration, according to the Physics Classroom. A heavier object hitting a lighter object will cause the lighter object to accelerate faster than a reverse example. A 20-lb ball, for example, rolling at 5-mph, on a flat surface, and into an 8-lb ball, will cause the 8-lb ball to roll faster than if the 8-lb ball rolls at 5-mph, on a flat surface, into a 20-lb. ball.
Gravitational-force is relative to the natural pressure and speed exerted upon an object in free-fall, according to Merriam-Webster. An object in free-fall will gain speed due to the object's mass and the pull of gravity, while air resistance, according to "Science Kids," creates drag on the object -- thus slowing the object's potential free-fall speed. A race car driver, for example, may experience a maximum of 5 g-forces while pushing the breaks on his car -- and in excess of 100 g-forces if he were to hit a track wall head on and come to a dead stop.