Here's why:
* Newton's First Law of Motion: An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.
* Constant speed: The car is not accelerating, meaning its velocity is not changing.
* Acceleration and Force: Acceleration is caused by a net force. If there is no acceleration, there is no net force.
Therefore, if a car is moving in a straight line at a constant speed, the forces acting on it must be balanced, resulting in a net force of zero.
Note: Even though there is no net force, there are likely forces acting on the car. For example:
* Forward force: This is the force from the engine that propels the car.
* Friction: This opposes the motion of the car (air resistance, friction from the tires on the road).
* Gravity: This pulls the car downwards, but is counteracted by the normal force from the road.
These forces are balanced, leading to a net force of zero.
