Net Force Examples in Physics

Start with the recap, study the fully worked examples, then use the practice problems to check your understanding of Net Force.

This page combines explanation, solved examples, and follow-up practice so you can move from recognition to confident problem-solving in Physics.

Concept Recap

The single resultant force obtained by vector addition of all individual forces acting on an object, which alone determines the object's acceleration according to Newton's second law.

What you get when you add up all pushes and pulls, accounting for direction.

Read the full concept explanation →

How to Use These Examples

  • Read the first worked example with the solution open so the structure is clear.
  • Try the practice problems before revealing each solution.
  • Use the related concepts and background knowledge badges if you feel stuck.

What to Focus On

Core idea: Only the net force determines acceleration, not individual forces.

Common stuck point: Forces in opposite directions subtract; forces in the same direction add.

Sense of Study hint: When you see a net force problem, first draw a free-body diagram and list every force with its direction. Then add forces in the same direction and subtract those in opposite directions. Finally, the net force determines the object's acceleration via F_{\text{net}} = ma.

Worked Examples

Example 1

easy
Three forces act on an object: 10 \text{ N} right, 4 \text{ N} left, and 3 \text{ N} left. What is the net force?

Solution

  1. 1
    Define right as positive. Forces: +10 \text{ N}, -4 \text{ N}, -3 \text{ N}.
  2. 2
    Sum the forces: F_{\text{net}} = 10 + (-4) + (-3) = 3 \text{ N}
  3. 3
    The net force is 3 \text{ N} to the right.

Answer

F_{\text{net}} = 3 \text{ N to the right}
Net force is the vector sum of all forces acting on an object. It determines the object's acceleration according to Newton's second law.

Example 2

medium
A 4 \text{ kg} object experiences forces of 20 \text{ N} forward and 8 \text{ N} backward. What is the net force and resulting acceleration?

Practice Problems

Try these problems on your own first, then open the solution to compare your method.

Example 1

medium
Two perpendicular forces act on an object: 6 \text{ N} east and 8 \text{ N} north. What is the magnitude of the net force?

Example 2

easy
A 10 \text{ kg} sled accelerates east at 1.5 \text{ m/s}^2. What is the net force on the sled?
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Background Knowledge

These ideas may be useful before you work through the harder examples.

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