In the real world, it is difficult to find a situation where no forces are acting on an object. But by applying additional forces, a condition can be achieved where the net force on the object is zero. Explain with the help of an example.
In the real world, multiple forces act on an object simultaneously. However, by applying an additional force, we can create a condition where the net force on the object becomes zero.
For example, consider a moving box on a floor. A force of friction acts on it in the backward direction. If a person pushes the box in the forward direction with a force equal to the frictional force, the two forces are equal and opposite. They balance each other, making the net force zero. Consequently, the box will continue moving with a constant velocity.
Explanation
The textbook explains that in real life, situations seldom exist where only one force acts on an object (Section 6.2). To achieve a net force of zero, additional forces must be applied to balance the existing ones. Example 6.2 perfectly illustrates this: a moving box experiences a backward frictional force, but when a person applies an equal forward force, the forces balance each other out. This results in a net force of zero, and as per Newton's first law, the object continues to move with constant velocity. Another example from the text is a ball floating on water, where the downward gravitational force is balanced by the upward buoyant force.