**The mass of an object does not affect its speed along an inclined plane, presuming that the object's mass does not prevent it from moving altogether.** Only the force of gravity, the angle of the incline and the coefficient of friction influence the object's speed.

A free-body diagram of the situation verifies this conclusion. According to Newton's laws, the sum of the forces in the y direction equals zero because the object is not falling through the plane. The normal force is equal to the product of the mass of the object, the acceleration due to gravity and the cosine of the angle of inclination.

The sum of the forces in the x direction equals the difference of the product of the mass of the object, the acceleration due to gravity, and the sine of the angle of inclination with the product of the coefficient of kinetic friction, the mass of the object, the acceleration due to gravity and the cosine of the angle of inclination. This difference is equal to the product of the mass of the object with its acceleration.

The object's mass does not influence the speed because it is divided out of each term.