6. Intro to Forces (Dynamics)

A tire swing hangs from a tree branch by a rope. Identify all the forces acting on the tire.

You push a couch across a carpeted (rough) living room floor. Identify all the forces acting on the couch.

A ball is hanging from a long string that is tied to the ceiling of a train car traveling eastward on horizontal tracks. An observer inside the train car sees the ball hang motionless. Draw a clearly labeled free-body diagram for the ball if the train is speeding up uniformly. Is the net force on the ball zero in either case? Explain.

Crates $A$ and $B$ sit at rest side by side on a frictionless horizontal surface. They have masses $m_A$ and $m_B$, respectively. When a horizontal force $F$ is applied to crate $A$, the two crates move off to the right. 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.

(I) A 650-N force acts in a northwesterly direction. A second 650-N force must be exerted in what direction so that the resultant of the two forces points westward? Illustrate your answer with a vector diagram.

A $1130$-kg car is held in place by a light cable on a very smooth (frictionless) ramp (Fig. E$5.8$). The cable makes an angle of $31.0°$ above the surface of the ramp, and the ramp itself rises at $25.0°$ above the horizontal. Draw a free-body diagram for the car.