Applied force

Frictional force

Net force

In the SI system of measurement, the unit of force is the **Newton**. The Newton unit is derived during the calculation of force using the equation F=ma. In this equation "F" is force, "m" is mass, and "a" is acceleration. When mass is measured in kilograms and acceleration is measured in m/s2, then the force will be calculated in Kgm/s2 or Newtons. 1 Newton is equal to 1Kgm/s2. A **Newton** of force is the amount of applied force required to accelerate a 1kg mass at a rate of 1m/s2. The following diagram illustrates this relationship.

Look at the problems below. Determine the force, mass, or acceleration, in each.

Example #1: How much force is required to accelerate a 2000kg car at 3.0m/s2?

Solution:

In this first example the Unit of force, the Newton, is derived using dimensional analysis. By multiplying "kg" times "m/s2", no units cancel. They must all appear in the answer. Remember, 1kgm/s2 is equal to a Newton force.

Example #2: A kicker applies a force of 300N to a .454kg soccer ball. What is the acceleration of the ball?

Solution:

In example #2 above, the Unit of acceleration, m/s2, is derived using dimensional analysis. By dividing the Newton force unit ( Remember a Newton is actually a kgm/s2 !), by kilogram mass units, the kilogram unit cancels, leaving only acceleration units of m/s2. The unit that appears in the answer is m/s2. Remember, a Newton is actually a kgm/s2.

Example #3: What is the mass of a cart that is accelerated at 2.5m/s2 by a 30N force?

Solution:

In example #3 above, the Unit of mass, the kg, is derived using dimensional analysis. By dividing the Newton force unit ( Remember a Newton is actually a kgm/s2.), by the m/s2 acceleration unit, the m/s2 unit cancels, leaving only mass units of kilograms in the answer!