IIsaac Newton and his three laws of equation
1.Every object continues to rest or continue to move in a straight line until a force acts on it .
2.When a net force acts on object of constant mass,an acceleration will result with the product of its mass and acceleration equal to the net force,the direction of the acceleration willbeing in the same direction as that of the net force For example,if in a tug of war,both sides pulls with equal force,nothing happens.But if one team exerts a larger force than the other,both teams accelerate in the directionof this larger force.
3.If A pushes to B, to the rightB pushes to A to the left with the same size of the force.Normally,this type of force will stay at rest or keep going at the constant speed.
backnewton_and_the_introduction_of_m.htm to Albert Einstein