Free Body Diagram of a Car Going Downhill

Introduction

A free body diagram (FBD) is a diagram that shows all the forces acting on an object. It is a useful tool for understanding how an object will move. In this case, we will draw a FBD for a car going downhill.

Assumptions

We will assume that the following forces are acting on the car:

• Weight (mg)
• Normal force (N)
• Friction force (f)
• Air resistance (D)

Diagram

The FBD for the car going downhill is shown below.

    m g
    |
    |
    N
    -----
    /     
    f      D
  

Analysis

The weight of the car is the force of gravity pulling it down. The normal force is the force of the road pushing up on the car. The friction force is the force that opposes the car’s motion. The air resistance is the force that opposes the car’s motion due to the air.

The net force acting on the car is the sum of all the forces acting on it. In this case, the net force is:

    F_net = m g - N - f - D
  

If the net force is positive, the car will accelerate downhill. If the net force is negative, the car will decelerate downhill. If the net force is zero, the car will move at a constant speed.

Conclusion

The FBD for a car going downhill is a useful tool for understanding how the car will move. By considering all of the forces acting on the car, we can determine the net force and predict the car’s acceleration.