Chapter 6 - Dynamics I: Motion Along a Line - Conceptual Questions - Page 153: 16

Since the crate moves without slipping, the force of static friction is causing the crate to accelerate at the same rate as the truck. Since the crate is accelerating toward the north, then the friction force must point toward the north.

Since the crate moves without slipping, the force of static friction is causing the crate to accelerate at the same rate as the truck. Since the crate is accelerating toward the north, then the friction force must point toward the north.