Question

The free-body diagrams of four objects are shown.

Four free body diagrams are shown. The first free body diagram is labeled W with 4 force vectors. The first vector is pointing downward, labeled F Subscript g Baseline = negative 15 N. The second vector is pointing right, labeled F Subscript p Baseline = 10 N. The third vector is pointing upward, labeled F Subscript N Baseline = 20 N. The fourth vector is pointing left, labeled F Subscript f Baseline = negative 10 N. The upward vector is longer than the downward vector. The right vector is the same length as the left vector. The second free body diagram is labeled X with 4 force vectors. The first vector is pointing downward, labeled F Subscript g Baseline = negative 25 N. The second vector is pointing right, labeled F Subscript p Baseline = 15 N. The third vector is pointing upward, labeled F Subscript N Baseline = 20 N. The fourth vector is pointing left, labeled F Subscript f Baseline = negative 15 N. The upward vector is shorter than the downward vector. The right and left vectors are the same length. The third free body diagram is labeled Y with 4 force vectors. The first vector is pointing downward, labeled F Subscript g Baseline = negative 10 N. The second vector is pointing right, labeled F Subscript p Baseline = 10 N. The third vector is pointing upward, labeled F Subscript N Baseline = 10 N. The fourth vector is pointing left, labeled F Subscript f Baseline = negative 15 N. The upward vector is the same length as the downward vector. The right vector is shorter than the left vector. The fourth free body diagram is labeled Z with 4 force vectors. The first vector is pointing downward, labeled F Subscript g Baseline = negative 15 N. The second vector is pointing right, labeled F Subscript p Baseline = 20 N. The third vector is pointing upward, labeled F Subscript N Baseline = 15 N. The fourth vector is pointing left, labeled F Subscript f Baseline = negative 10 N. The upward vector is the same length as the downward vector. The right vector is longer than the left vector.

Which object has a net force of –5 N down?

W
X
Y
Z

Answer 1

X

Reason: net vertical force = N (up) + Fg (down). For X: 20 N + (−25 N) = −5 N (down). W: +5 N up, Y and Z: 0 N.