What does a free-body diagram show?

Arrows representing each force exerted on an object or system by its environment.

What do the length and direction of a force arrow represent in a free-body diagram?

Length: the magnitude of the force, drawn proportional to it Direction: the direction of the force

Where do the force arrows originate in a free-body diagram?

At the object's or system's center of mass .

What is the purpose of a coordinate system on a free-body diagram, and how is it positioned?

It simplifies the translation from a free-body diagram to an algebraic representation One axis is parallel to the direction of acceleration The two axes are perpendicular to each other

On an inclined plane, the normal force always acts .......... to the slope.

On an inclined plane, the normal force always acts perpendicular to the slope.

True or False? On the free-body diagram of a car accelerating along a level road, the thrust and friction arrows are equal in length.

False. The car is accelerating, so there is a net force forward. The thrust arrow must be longer than the friction arrow.

A force is a push or pull due to the interaction of an object or system with another object or system.

Define contact forces .

Contact forces describe the interaction of an object or system touching another object or system. They are macroscopic effects of interatomic electric forces .

Name examples of contact forces .

Normal (reaction) force Tension Kinetic and static friction Thrust and upthrust

How do interatomic electric forces produce contact forces?

When objects touch, the atoms at their surfaces interact through electric forces. When two atoms are close, their electrons repel each other, causing a strong repulsive force.

When does a fluid exert an upthrust on an object?

When the object is fully or partially submerged in the fluid. The fluid exerts an upward-acting push force on the object.

Define normal force .

The normal force is the perpendicular component of the force exerted on an object by the surface it is in contact with, directed away from the surface.

.......... is a force produced by an engine that speeds up the motion of an object.

Thrust is a force produced by an engine that speeds up the motion of an object.

True or False? The normal force on an object always points vertically upward.

False. The normal force is always perpendicular to the surface . On an inclined plane it is not vertical.

The net force on a system is the vector sum of all forces exerted on the system. It is also called the resultant force .

What does the net force on a system determine?

Whether the system's direction of motion changes Whether the system's speed changes

What is the net force on a system when the forces are balanced and when they are unbalanced ?

Balanced: the net force is zero (the system is in translational equilibrium) Unbalanced: the net force is not equal to zero

In a tug-of-war, person A pulls a rope with 80 N to the left and person B pulls with 100 N to the right. What is the net force on the rope?

20 N to the right , because the forces are unbalanced and do not cancel completely.

An object or system cannot exert a .......... force on itself.

An object or system cannot exert a net force on itself.

True or False? Balanced forces mean that no forces act on the system.

False. Forces still act on the system. Their vector sum is zero, so the net force is zero.

Define translational equilibrium .

Translational equilibrium is a configuration of forces such that the net force exerted on a system is zero .

How can an object in translational equilibrium be moving?

Only at a constant velocity (constant speed in the same direction), because with no net force there is no change in the object's motion.

Name the forces on an object sliding down a rough slope at constant velocity.

Weight Normal force from the slope Friction from the slope, acting up the slope

In translational equilibrium, the force vectors are arranged .......... so that their vector sum is zero.

In translational equilibrium, the force vectors are arranged tip-to-tail so that their vector sum is zero.

True or False? An object moving at constant velocity has a net force in the direction of motion.

False. An object moving at constant velocity is in translational equilibrium, so the net force is zero .

AP®PhysicsCollege BoardPhysics 1: Algebra-BasedFlashcardsUnit 2: Force & Translational DynamicsForces & Free-Body Diagrams

Forces & Free-Body Diagrams (College Board AP® Physics 1: Algebra-Based): Flashcards

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FrontFree Body Diagrams
What does a free-body diagram show?
FrontFree Body Diagrams
What do the length and direction of a force arrow represent in a free-body diagram?
BackFree Body Diagrams
Length: the magnitude of the force, drawn proportional to it
Direction: the direction of the force

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Cards in this collection (30)

What does a free-body diagram show?
Arrows representing each force exerted on an object or system by its environment.
What do the length and direction of a force arrow represent in a free-body diagram?
- Length: the magnitude of the force, drawn proportional to it
- Direction: the direction of the force
Where do the force arrows originate in a free-body diagram?
At the object's or system's center of mass.
How can each force arrow in a free-body diagram be labeled?
- A description of the force, including the objects interacting
- The name of the force, e.g. weight
- An appropriate symbol, e.g. $F_{g}$
What is the purpose of a coordinate system on a free-body diagram, and how is it positioned?
- It simplifies the translation from a free-body diagram to an algebraic representation
- One axis is parallel to the direction of acceleration
- The two axes are perpendicular to each other
What are the components of an object's weight parallel and perpendicular to an incline at angle $θ$ ?
- Parallel: $F_{g} sin θ$
- Perpendicular: $F_{g} cos θ$
On an inclined plane, the normal force always acts .......... to the slope.
On an inclined plane, the normal force always acts perpendicular to the slope.
True or False?
On the free-body diagram of a car accelerating along a level road, the thrust and friction arrows are equal in length.
False.
The car is accelerating, so there is a net force forward. The thrust arrow must be longer than the friction arrow.
Define force.
A force is a push or pull due to the interaction of an object or system with another object or system.
Name four properties of an object that a force can affect.
- Speed
- Direction
- Shape
- Size
Define contact forces.
Contact forces describe the interaction of an object or system touching another object or system. They are macroscopic effects of interatomic electric forces.
Name examples of contact forces.
- Normal (reaction) force
- Tension
- Kinetic and static friction
- Thrust and upthrust
How do interatomic electric forces produce contact forces?
When objects touch, the atoms at their surfaces interact through electric forces. When two atoms are close, their electrons repel each other, causing a strong repulsive force.
When does a fluid exert an upthrust on an object?
When the object is fully or partially submerged in the fluid. The fluid exerts an upward-acting push force on the object.
Define normal force.
The normal force is the perpendicular component of the force exerted on an object by the surface it is in contact with, directed away from the surface.
.......... is a force produced by an engine that speeds up the motion of an object.
Thrust is a force produced by an engine that speeds up the motion of an object.
True or False?
The normal force on an object always points vertically upward.
False.
The normal force is always perpendicular to the surface. On an inclined plane it is not vertical.
Define net force.
The net force on a system is the vector sum of all forces exerted on the system. It is also called the resultant force.
What does the net force on a system determine?
- Whether the system's direction of motion changes
- Whether the system's speed changes
What is the net force on a system when the forces are balanced and when they are unbalanced?
- Balanced: the net force is zero (the system is in translational equilibrium)
- Unbalanced: the net force is not equal to zero
In a tug-of-war, person A pulls a rope with 80 N to the left and person B pulls with 100 N to the right. What is the net force on the rope?
20 N to the right, because the forces are unbalanced and do not cancel completely.
An object or system cannot exert a .......... force on itself.
An object or system cannot exert a net force on itself.
True or False?
Balanced forces mean that no forces act on the system.
False.
Forces still act on the system. Their vector sum is zero, so the net force is zero.
Define translational equilibrium.
Translational equilibrium is a configuration of forces such that the net force exerted on a system is zero.
How can an object in translational equilibrium be moving?
Only at a constant velocity (constant speed in the same direction), because with no net force there is no change in the object's motion.
State the equation for translational equilibrium.
$\sum_{i} {\vec{F}}_{i} = 0$
- ${\vec{F}}_{i}$ = each force exerted on the system (N)
How is the equation for translational equilibrium derived from Newton's second law?
- The object is at rest or moving at constant velocity, so $\vec{a} = 0$
- Newton's second law then gives ${\vec{F}}_{net} = m \vec{a} = 0$
- So the vector sum of the forces is zero, $\sum_{i} {\vec{F}}_{i} = 0$
Name the forces on an object sliding down a rough slope at constant velocity.
- Weight
- Normal force from the slope
- Friction from the slope, acting up the slope
In translational equilibrium, the force vectors are arranged .......... so that their vector sum is zero.
In translational equilibrium, the force vectors are arranged tip-to-tail so that their vector sum is zero.
True or False?
An object moving at constant velocity has a net force in the direction of motion.
False.
An object moving at constant velocity is in translational equilibrium, so the net force is zero.

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