Kaplan Nursing Entrance Practice Exam

When pushing a heavy box across the floor, which statement is true?

1. The force required to start sliding is less than to keep sliding

2. Pushing without movement results in work being done

3. The coefficient of static friction is not dependent on surface nature

4. All of the above

The correct answer is: All of the above

The correct answer reflects the understanding of friction and work in physics. When pushing a heavy box across the floor, it is true that the force required to start sliding (overcoming static friction) is generally less than the force needed to keep it sliding (overcoming kinetic friction). This concept is grounded in mechanics; static friction usually has a higher maximum threshold than kinetic friction, making it easier to maintain movement once it has begun. Furthermore, it is important to note that work is defined in physics as force applied over a distance. In the situation described, pushing without any movement means there is no displacement, and consequently, no work is being done according to the physics definition. This aligns with understanding how force and motion interact. Regarding the coefficient of static friction, it does depend on the nature of the surfaces in contact. Different materials will have different coefficients of friction based on their textures and materials; this means that the statement implying the coefficient of static friction is not dependent on surface nature is inaccurate. Thus, while the answer suggests a collective truth in all statements, it is insightful to recognize that the first part regarding the comparison of static and kinetic friction holds true, reinforcing why the entire statement claims all are correct.