Question

which free body diagram best shows the forces acting on the box at time 4 1 point when it is moving but slowing down? (blue vector is force from cart, red vector is force of friction, and green vector is force of air resistance.)

Explanation:

Step1: Analyze the motion

When the box is moving but slowing down, the net force is opposite to the direction of motion. Assuming the box is moving to the right (since the blue force from the cart is a common driving force, often in the direction of intended motion). The forces of friction (red) and air - resistance (green) act opposite to the direction of motion (to the left). The blue force (from the cart) is in the direction of motion (to the right). But since it is slowing down, the sum of the resistive forces (friction + air - resistance) is greater than the blue force.

Step2: Check each option

• Option A: No blue force (force from cart), so it cannot be correct as the cart is presumably still exerting some force (even if it's less than resistive forces).
• Option B: Blue force is very small (maybe negligible in the diagram's scale), and the sum of red (friction) and green (air - resistance) forces (both to the left) can create a net force to the left (opposite to the assumed direction of motion, causing deceleration).
• Option C: Blue force (to the right) is larger than the sum of red and green forces (to the left), which would cause acceleration, not deceleration.
• Option D: Forces are in the wrong direction for deceleration (if we assume the motion direction based on the blue force's typical role as a driving force).

Answer:

B.