Which factor contributes directly to the amount of frictional force experienced by an object?

The amount of frictional force experienced by an object is directly influenced by the mass of the object. Friction is primarily dependent on the normal force, which is a force perpendicular to the contact surface. For objects resting on a horizontal surface, this normal force is equivalent to the weight of the object, which is the product of the masses and the acceleration due to gravity. Therefore, as the mass of the object increases, its weight increases, subsequently increasing the normal force and, as a result, increasing the frictional force.

While surface area, speed, and temperature can have roles in specific scenarios involving friction, they do not directly affect the frictional force in the most common cases. The frictional force is determined mainly by the surfaces in contact and the weight of the object, making mass the key factor in this context.