A girl weighing 400 N climbs a vertical ladder. If the value of g be 10 m/s² the work done by her after climbing 2m will be. 

Calculation:

The work done (W) is calculated using the formula:In this case, the force is the weight of the girl, which is (400 N), the distance is the height climbed, which is2m, and the angle is 0°  because the force is acting vertically upward, and the displacement is also vertical.

\( W = \text{force} \times \text{distance} \times \cos(\theta) \)

The cosine of 0 degrees is 1, so the equation simplifies to:\([ W = 400 \, \text{N} \times 2 \, \text{m} \times \cos(0^\circ) \)

\( W = 400 \, \text{N} \times 2 \, \text{m} \times 1 \)

\( W = 800 \, \text{N} \cdot \text{m} \)

Since \(1 \, \text{N} \cdot \text{m} = 1 \, \text{J}\),

 the work done is (800 J)

Therefore, the correct answer is: 800 J