A body of mass 20 kg is kept initially at rest. A force of 80 N is applied on the body then the acceleration produced in the body is `3 m//s^(2)`, force of friction acting on the body is :

Options

A. 80 N
B. 12 N
C. 20 N
D. Zero

Explanation

To solve the problem, we will use Newton's second law of motion, which states that the net force acting on an object is equal to the mass of the object multiplied by its acceleration.

### Step-by-step Solution:

1. **Identify the Given Values:**
- Mass of the body (m) = 20 kg
- Applied force (F_applied) = 80 N
- Acceleration (a) = 3 m/s²

2. **Write the Equation for Net Force:**
According to Newton's second law:
\[ F_{net} = m \cdot a \]
Here, \(F_{net}\) is the net force acting on the body.

3. **Calculate the Net Force:**
Substitute the values of mass and acceleration into the equation:
\[ F_{net} = 20 \, \text{kg} \cdot 3 \, \text{m/s}^2 = 60 \, \text{N} \]

4. **Set Up the Equation for Forces:**
The net force is also the difference between the applied force and the frictional force (F_friction):
\[ F_{net} = F_{applied} - F_{friction} \]
Therefore:
\[ 60 \, \text{N} = 80 \, \text{N} - F_{friction} \]

5. **Solve for the Frictional Force:**
Rearranging the equation gives:
\[ F_{friction} = 80 \, \text{N} - 60 \, \text{N} = 20 \, \text{N} \]

6. **Conclusion:**
The force of friction acting on the body is **20 N**.