Crates A and B sit at rest side by side on a frictionless horizontal surface. They have masses mA and mB, respectively. When a horizontal force is applied to crate A, the two crates move off to the right. (a) Draw clearly labeled free-body diagrams for crate A and for crate B. Indicate which pairs of forces, if any, are third-law action–reaction pairs. (b) If the magnitude of is less than the total weight of the two crates, will it cause the crates to move? Explain.
Solution 27E Step 1: a) Figure 1 represents the free body diagram of crate A and B. In both of these, the gravitational force and normal force are action reaction pairs according to the Newton’s third law.