A Car is Stopped at a Stoplight: Free Body Diagram
Introduction
When a car is stopped at a stoplight, it is in equilibrium. This means that the net force acting on the car is zero. In this post, we will draw a free body diagram of a car stopped at a stoplight and identify all of the forces acting on the car.
Free Body Diagram
A free body diagram is a diagram that shows all of the forces acting on an object. The forces are represented by vectors, which have both magnitude and direction. The net force acting on an object is the vector sum of all the forces acting on the object.
The free body diagram of a car stopped at a stoplight is shown below.
Forces Acting on the Car
The following forces are acting on the car:
- Gravity: Gravity is a force that pulls the car down towards the ground. The force of gravity is equal to the mass of the car times the acceleration due to gravity (g = 9.8 m/s^2).
- Normal force: The normal force is a force that the ground exerts on the car. The normal force is equal to the weight of the car (mg). The normal force acts perpendicular to the surface of the ground.
- Friction: Friction is a force that opposes the motion of the car. Friction is caused by the interaction between the tires of the car and the road. Friction acts in the opposite direction of the car’s motion.
Net Force
The net force acting on the car is zero. This means that the sum of the forces in the x-direction is zero and the sum of the forces in the y-direction is zero.
$$sum F_x = 0$$
$$sum F_y = 0$$
Conclusion
The free body diagram of a car stopped at a stoplight shows that the net force acting on the car is zero. This is because the forces of gravity, normal force, and friction are all balanced.
