If the coefficient of kinetic friction between a 12.0 kg crate and the floor is .30, what horizontal force is required to move the crate at a steady speed across the floor? What horizontal force is required if the force of friction is zero?
Newton's first law states that the total force applied to a body must be zero if the body is at rest or moving with constant velocity.
In this case we have to apply this law in both vertical and horizontal directions.
The forces applied on the obect are ...
In the first case, the solution is found by applying Newton's first law in both vertical and horizontal directions.