A trash can is dragged rightward across pavement. Which set of arrows is its correct free-body diagram?
A car rounds a flat curve at a steady speed. You can name its supplier now: friction. But a full analysis needs more than a name. It needs the car's free-body diagram, with every force drawn, and the drawing has to show one thing above all: a net force pointing at the curve's center.
You have drawn free-body diagrams before: the object as a box, every real force as a labeled arrow with its tail at the object. Circular motion changes none of that. It adds one check at the end.
Here is the turning car, seen from behind, with the center of the turn to its left.
Step 1: list the real forces and their sources. Earth exerts the weight, straight down. The road presses up on the tires: the normal force. The road grips the tires sideways, toward the center of the turn: friction.
Step 2: draw one labeled arrow per force, every tail at the car. Only real forces get arrows. No 'centripetal force' arrow is added, because no such separate force acts.
Step 3: check the net force. The weight and the normal force are vertical and cancel. The friction is unbalanced, and it points toward the center. The net force points at the center, exactly as uniform circular motion requires.
A tow truck rounds a flat corner at a steady speed. Which set of arrows belongs on its free-body diagram?
A car rounds a flat curve at a steady speed, with the curve's center to its left. List the forces for its free-body diagram, and state the net force.
List the real forces and their sources: Earth exerts the weight, down; the road presses the car up (the normal force); the road's friction acts on the tires, toward the center.
Draw the three labeled arrows, tails at the car. No other arrow: no separate 'centripetal force' acts.
Check the net force: the weight and the normal force cancel; the friction is unbalanced, toward the center.
Three arrows: weight down, normal force up, friction toward the center. The net force is the friction, pointing at the curve's center.
A wagon circles on a flat plaza at a steady speed, gripped by the pavement. On its free-body diagram, which two arrows cancel each other?
One note about these diagrams: ignore drag. The air's force on a vehicle at these speeds is small enough to leave out, so it gets no arrow.
A puck on a frictionless table circles a center peg at the end of a cord. List the forces for its free-body diagram, and state the net force.
List the real forces and their sources: Earth exerts the weight, down; the table presses the puck up (the normal force); the cord's tension acts toward the peg.
Draw the three labeled arrows, tails at the puck; the table is frictionless, so no friction arrow.
Check the net force: the weight and the normal force cancel; the tension is unbalanced, toward the peg at the center.
Three arrows: weight down, normal force up, tension toward the peg. The net force is the tension, pointing at the center.
For a jeep rounding a flat bend at a steady speed, Minna draws: weight down, the normal force up, friction toward the bend's center, and no other arrows. Is her diagram correct?
A rider circles inside a spinning fair ride, pressed against its vertical wall, feet off the floor. Which set of arrows belongs on the rider's free-body diagram?
A roller skate circles a stake on a cord over smooth ice. Its free-body diagram shows weight down, the ice's normal force up, and the cord's tension toward the stake. What is the net force on the skate?
Seen from above, a model boat sails a circular course at a steady speed and is at the easternmost point of the circle. In which direction does the net force on the boat point at that instant?