Question

a. three blocks are pushed along a rough surface by a force with magnitude p, as shown below.

diagram of three blocks: block 1, block 2, block 3, with force p pushing block 1 from the left

$f_1$ is the magnitude of the contact force between blocks 3 and 1, and $f_f$, $f_n$, and $f_g$ are the magnitudes of the friction, normal, and gravitational forces on block 1, respectively. which of the following is a correct free - body diagram for block 1?

a. diagram with $f_n$ up, $f_g$ down, $p$ right, $f_c$ right, $f_f$ left
b. diagram with $f_n$ up, $f_g$ down, $p$ right, $f_c$ left
c. diagram with $f_n$ up, $f_g$ down, $f_c$ right, $f_f$ left
d. diagram with $f_n$ up, $f_g$ down, $f_g$ right (note: likely a typo, maybe $f_f$ or other force)

Explanation:

1. Vertical forces on Block 3: The upward normal force $F_N$ balances the downward gravitational force $F_G$.
2. Horizontal forces on Block 3: Block 3 is pushed by Block 2, so it experiences a rightward contact force $F_C$. Since the surface is rough, there is a leftward kinetic friction force $F_f$ opposing the motion. The external force $P$ does not act directly on Block 3.

Answer:

C. The free-body diagram with upward $F_N$, downward $F_G$, rightward $F_C$, and leftward $F_f$