Answer :
Final answer:
The net work done on the box is calculated using the work-energy principle and is equal to the change in kinetic energy. After using the kinematic equation to find the final velocity, the final kinetic energy is calculated as 392 J, meaning the net work done is also 392 J. Therefore the correct answer is: d).
Explanation:
This principle states that the work done on an object is equal to the change in its kinetic energy. Since the box starts from rest, its initial kinetic energy is 0. After 7 seconds, we can calculate the final velocity of the box using the kinematic equation v = at, where v is the final velocity, a is the acceleration, and t is the time. Substituting in the values provided, we get v = 2.0 m/s² × 7.0 s = 14.0 m/s.
The final kinetic energy (KE) of the box can be found using the formula KE = ½ mv², where m is the mass and v is the final velocity. Here, KE = ½ × 4.0 kg × (14.0 m/s)² = 392 Joules (J). Since the initial kinetic energy was 0 J, the change in kinetic energy, which is the work done on the box, is 392 J. Thus, the net work done is 392 J.
Work-energy theorem is a fundamental principle in physics that relates the work done on an object to the change in its kinetic energy. It states that the work done on an object by the net force acting on it is equal to the change in its kinetic energy.
