Gravity is a natural force that pulls all objects toward the center of the Earth. Gravity has a stronger force on objects with greater mass, so while a bouncy ball and marble fall at the same rate of speed due to gravity, the marble experiences a harder fall due to its greater mass. Gravity also requires the application of greater force to overcome for objects with higher mass, as it is harder to throw a basketball into the air than a bean bag due to the basketball's larger mass.