According to Newton’s first law, if no force acts on an object, it will just continue moving. Explain in terms of Newton’s first law why a car engine must exert a force between the car and the road to drive at a constant speed on a straight and level road.
The correct answer and explanation is:
Correct Answer:
According to Newton’s first law, a car engine must exert a force between the car and the road to overcome resistive forces like friction and air resistance, so the car can maintain a constant speed on a straight and level road.
Explanation (300 words):
Newton’s first law of motion, also called the law of inertia, states that an object will remain at rest or continue to move at a constant velocity in a straight line unless acted upon by an external force. This means that no change in motion (acceleration or deceleration) will occur unless there is a net force acting on the object.
When a car moves on a straight and level road, it may seem like it should keep moving without any additional force. However, in reality, there are always forces acting against its motion. These include friction from the contact between the tires and the road, as well as air resistance pushing against the forward motion of the car. These resistive forces act in the opposite direction of the car’s motion and tend to slow it down.
To prevent the car from slowing down due to these opposing forces, the engine must provide a forward force. This force is transmitted through the wheels and creates friction between the tires and the road surface. This frictional force allows the car to push against the road and move forward. When the engine provides just enough force to balance the resistive forces, the net force on the car becomes zero. In this state, according to Newton’s first law, the car will continue to move at a constant speed in a straight line.
So, even though no acceleration is involved, the engine must continuously supply force to maintain the car’s speed and direction. Without this engine force, the car would eventually slow down and stop due to the unbalanced resistive forces acting on it.