A box is moved 20 m across a smooth floor by a force making a downward angle with the floor, so that there is effectively a 10 N force acting parallel to the floor in the direction of motion and a 5 N force acting perpendicular to the floor the work done is:

100 J

Explanation:

From the question, The work done by the forces in moving the box is given as

W = FxdcosФ+Fydcosα Equation 1

Where W = Work done, Fx = force acting parallel to the floor, d = distance moved by the box, Ф = angle the parallel force makes with the floor, Fy = force acting perpendicular to the floor, α = angle the perpendicular force make with the floor.

Give: Fx = 10 N, d = 20 m, Fy = 5 N, Ф = 0°, α = 90°

Substitute into equation 1

W = 10×10×cos0°+5×20×cos90°

W = 10×10×1+0

W = 100 J.

Note: The work done by the perpendicular force is zero

Hence the work done = 100 J