A 120 N force is applied at an angle of 30.0 degrees above the horizontal to a 4.00 kg box on a frictionless surface. The box moves a horizontal distance of 8.00 meters. The change in the kinetic energy of the box is
A) 667 J.
B) 750 J.
C) 831 J.
D) 890 J.
E) 920 J.

Question

Quizplus · Accepted Answer

The change in kinetic energy can be calculated using the work-energy principle, where the work done on the object is equal to the change in its kinetic energy. The work done by the force is given by $W = Fd\cos(\theta)$, where $F$ is the force applied, $d$ is the distance moved, and $\theta$ is the angle of the force with the horizontal. Substituting the given values, $W = 120 \, \text{N} \times 8.00 \, \text{m} \times \cos(30^\circ) = 960 \times \sqrt{3}/2 \approx 831 \, \text{J}$.

A 120 N Force Is Applied at an Angle of 30.0