Something seems to be wrong here: Fnet > ma! But we know from Newton’s second law that ma must equal the unbalanced force (Fnet ). In this situation, Fnet is equal to 15 newtons (5.0 kg · 3.0 m/s 2 ), not to the applied force of 20. newtons. Where have 5.0 newtons gone? There is another force present that we have not considered: friction. Frictional forces are always present when two surfaces are in contact. The direction of a frictional force on an object is always opposite to the direction of the object’s motion. We will represent a frictional force by the symbol Ff . We now complete the diagram above by adding in the 5.0-newton frictional force: 9. A force of 50. newtons is used to drag a 10.-kilogram object across a horizontal table. If a frictional force of 15. newtons is present on the object, calculate (a) the unbalanced force on the object and (b) the acceleration of the object.
To calculate the unbalanced force on the object, we need to subtract the frictional force from the applied force:
Unbalanced force = Applied force - Frictional force
Unbalanced force = 50. N - 15. N
Unbalanced force = 35. N
To calculate the acceleration of the object, we can use Newton's second law:
Fnet = ma
35. N = 10. kg * a
a = 3.5 m/s^2
Therefore, the unbalanced force on the object is 35. N and the acceleration of the object is 3.5 m/s^2.