When an object is at rest, the value of **net force **(F_{net}) is equal to the sum of **normal force** (F_{N}) and the **force of gravity** (F_{g}). Using the formula of net force: **F**_{net}** = F**_{N}** + F**** _{g}**, the value of net force acting on an object can be calculated.

Here’s the formula of net force:

- When an object is at rest,
**F**_{net}**= F**_{N}**+ F**_{g}

- When an object is in motion,
**F**_{net}**= F**_{a}**+ F**_{f}**+ F**_{N}**+ F**_{g}

- When ‘n’ number of forces are acting on an object,
**F**_{net}**= F**_{1}**+ F**_{2}**+ F**_{3}**+ … + F**_{n}

Let’s solve some problems based on these formulas, so you’ll get a clear idea.

## Net Force Practice Problems

**Problem 1:** Consider one block resting on the floor. If this block is balanced by 6 N of normal force and 6 N of gravity force, then what is the value of net force acting on this block?

Solution:

Given data:

Normal force acting on a block, F_{N} = 6 N

Force of gravity acting on a block, F_{g} = -6 N (downward)

Net force acting on a block, F_{net} = ?

Using the formula of net force, (when an object is at rest)

F_{net} = F_{N} + F_{g}

F_{net} = 6 – 6

F_{net} = 0 N

Therefore, the net force acting on a block is **0 N**.

**Problem 2:** One book is lying on the desk. When a 15 N of force is applied on this book, a friction force of 5 N acts on it in the opposite direction. If this book is balanced by 20 N of normal force and gravity force, then calculate the value of net force acting on it.

Solution:

Given data:

Applied force acting on a book, F_{a} = 15 N

Friction force acting on a book, F_{f} = -5 N (left)

Normal force acting on a book, F_{N} = 20 N

Force of gravity acting on a book, F_{g} = -20 N (downward)

Net force acting on a book, F_{net} = ?

Using the formula of net force, (when an object is in motion)

F_{net} = F_{a} + F_{f} + F_{N} + F_{g}

F_{net} = 15 – 5 + 20 – 20

F_{net} = 10 N

Therefore, the net force acting on a book is **10 N**.

**Problem 3:** Two persons 1 and 2 are pulling the rope from opposite ends. The person 1 (standing on the right side) pulls the rope with a force of 40 N and the person 2 (standing on the left side) pulls the rope with a force of 15 N. Calculate the net force acting on the rope.

Solution:

Given data:

Force acting on the rope, F_{1} = 40 N

Force acting on the rope, F_{2} = -15 N (left)

Net force acting on the rope, F_{net} = ?

Using the formula of net force, (when ‘n’ number of forces are acting on an object)

F_{net} = F_{1} + F_{2}

F_{net} = 40 – 15

F_{net} = 25 N

Therefore, the net force acting on the rope is **25 N**.

**Problem 4:** One car gets stuck on the road and 6 persons are pushing this car towards the right direction. All 6 persons are pushing the car with the following forces: 3 N, 4 N, 5 N, 3 N, 7 N and 2 N. Calculate the net force acting on the car.

Solution:

Given data:

Force acting on the car, F_{1} = 3 N

Force acting on the car, F_{2} = 4 N

Force acting on the car, F_{3} = 5 N

Force acting on the car, F_{4} = 3 N

Force acting on the car, F_{5} = 7 N

Force acting on the car, F_{6} = 2 N

Net force acting on the rope, F_{net} = ?

Using the formula of net force, (when ‘n’ number of forces are acting on an object)

F_{net} = F_{1} + F_{2} + F_{3} + F_{4} + F_{5} + F_{6}

F_{net} = 3 + 4 + 5 + 3 + 7 + 2

F_{net} = 24 N

Therefore, the net force acting on the car is **24 N**.

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**Related:**

- Force Equation
- Normal Force Equation
- Applied Force Formula
- Magnetic Force Equation
- Centripetal Force Equation
- Centrifugal Force Equation
- Spring Force Equation
- Tension Force Formula
- Electric Force Equation

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