AP Physics 1 2.2: Free-Body Diagrams

Represent the forces acting on an object or system with a free-body diagram, including force direction, relative magnitude, and the chosen system boundary.

[Maximum number: 3]

Figure for Question 2.2.B—Describe the forces exerted on an object or system using a free-body diagram question 1 — AP Physics 1: Algebra-Based

(12 points, suggested time 25 minutes)
This problem explores how the relative masses of two blocks affect the acceleration of the blocks. Block A, of mass $m_{A}$ , rests on a horizontal tabletop. There is negligible friction between block A and the tabletop. Block B, of mass $m_{B}$ , hangs from a light string that runs over a pulley and attaches to block A, as shown above. The pulley has negligible mass and spins with negligible friction about its axle. The blocks are released from rest.

Now suppose neither block's mass is much greater than the other, but that they are not necessarily equal. The dots below represent block A and block B, as indicated by the labels. On each dot, draw and label the forces (not components) exerted on that block after release. Represent each force by a distinct arrow starting on, and pointing away from, the dot.

LO 3.A.2.1, SP 1.1; LO 3.A.3.1, SP 6.4 3 points
Now suppose neither block's mass is much greater than the other, but that they are not necessarily equal. The dots below represent block A and block B, as indicated by the labels. On each dot, draw and label the forces (not components) exerted on that block after release. Represent each force by a distinct arrow starting on, and pointing away from, the dot.

Figure for Answer to Question 2.2.B—Describe the forces exerted on an object or system using a free-body diagram question 1 — AP Physics 1: Algebra-Based

For a correct normal force on block A with acceptable label: $N, F_{\mathrm{N}}$ , "normal force,"
$F_{\text {table }}$ , "table force," or any other label indicating the force is "normal" or comes
from the table

1 point

For correct gravitational forces with acceptable label on both diagrams: $F_{\mathrm{g}}, F_{\text {grav }}, W$ ,
$m g, m_{\mathrm{A}} g$ , "gravity," "grav force," but NOT G or g, and no extraneous forces on
either diagram

1 point

For correct tension forces with acceptable label on both diagrams: "tension," "string
force," $F_{T}, F_{\text {tension }}, F_{\text {string }}, F_{S}, T$ , or some other label indicating that the force
comes from the string or from tension. NOT acceptable: $m_{B} g, F_{m_{B}}$ , "force from
block B" or other indications that the force is "created" by block B1 point

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2.2.B—Describe the forces exerted on an object or system using a free-body diagram question 1