Question

A push broom is being pushed down across a rough floor. The broom moves to the right.

A picture of a person standing pushing a broom downward at an angle to the right. There is a velocity vector below the head of the broom pointing right, labeled v.

What is the correct free body diagram of the broom?



A free body diagram with 4 force vectors. The first vector is pointing downward, labeled F Subscript g Baseline. The second is pointing right, labeled F Subscript p Baseline. The third vector is pointing upward, labeled F Subscript N Baseline. The fourth vector is pointing left, labeled F Subscript f. The upward vector is the same length as the downward vector. The right vector is the same length as the left vector.

A free body diagram with 3 force vectors. The first vector is pointing downward, labeled F Subscript g Baseline. The second vector is pointing right, labeled F Subscript p Baseline. The third vector is pointing upward, labeled F Subscript N Baseline. All three vectors are of equal length.

A free body diagram with 4 force vectors. The first vector is pointing downward, labeled F Subscript g Baseline. The second vector is pointing right, labeled F Subscript f Baseline. The third vector is pointing upward, labeled F Subscript N Baseline. The fourth vector is pointing up to the left, labeled F Subscript P Baseline.

A free body diagram with 4 force vectors. The first vector is pointing downward, labeled F Subscript g Baseline. The second vector is pointing left, labeled F Subscript f Baseline. The third vector is pointing upward, labeled F Subscript N Baseline. The fourth vector is pointing down to the right, labeled F Subscript P Baseline. All vectors are the same length.

Answer 1

The fourth diagram is correct.

Reason: the person applies a force P down and to the right along the handle, so P points down-right. The floor exerts a normal force N upward. Gravity mg acts downward. Kinetic friction acts opposite the direction of motion, i.e. to the left. (If the broom moves with constant speed the leftward friction equals the rightward horizontal component of P; N = mg + the downward component of P.)