Answer :
Final answer:
The work done in keeping the uniform rod vertical with one of its ends touching the ground is b. 392 J.
Explanation:
The work done in keeping the uniform rod vertical with one of its ends touching the ground can be calculated by finding the difference in potential energy between the initial horizontal position and the vertical position. Since the rod is initially horizontal, its center of mass is at a height of 0.5 times its length, which is 2 m. When the rod is vertical, its center of mass is at a height of 2 m. Thus, the change in height is 2 m. The work done is given by the formula:
Work = Force × Distance × cos(θ)
where the force is the weight of the rod (mass × gravitational acceleration), the distance is the change in height, and θ is the angle between the force and the displacement. Plugging in the values:
Work = (20 kg × 9.8 m/s^2) × 2 m × cos(90°)
Work = 392 J
Therefore, the correct answer is option b. 392J.
