Define linear momentum .

Linear momentum is the product of an object's mass and its velocity .

Is momentum a scalar or a vector quantity?

Momentum is a vector quantity, so it has both magnitude and direction.

Momentum has the same direction as the object's .......... .

Momentum has the same direction as the object's velocity .

How does momentum differ from inertia ?

Momentum changes if the object's mass or velocity changes Inertia changes only if the object's mass changes An object at rest has inertia but zero momentum

True or False? Two objects with different masses can have the same momentum.

True. A light object moving fast can have the same momentum as a heavy object moving slowly, because momentum depends on both mass and velocity .

State Newton's second law in terms of momentum.

The rate of change of momentum is equal to the net external force exerted on an object (or system).

Impulse is the product of the average force exerted on an object and the time interval over which the force acts.

Is impulse a scalar or a vector quantity?

Impulse is a vector quantity, so it has both magnitude and direction.

Impulse has the same direction as the .......... force exerted on the system.

Impulse has the same direction as the net force exerted on the system.

How do seat belts and airbags reduce the force on a passenger in a collision?

They increase the collision time . The impulse is constant, so the average force decreases.

True or False? Impulse and force are equivalent quantities.

False. Impulse is the effect of a force acting over a time interval , so it is measured in N·s, not N.

State the impulse–momentum theorem .

The impulse exerted on a system is equal to the change in momentum of the system.

For a given change in momentum, a small force acting over a .......... time has the same effect as a large force acting over a short time.

For a given change in momentum, a small force acting over a long time has the same effect as a large force acting over a short time.

True or False? A crumple zone reduces the change in momentum of a car in a crash.

False. The change in momentum is the same with or without a crumple zone. The crumple zone increases the collision time , which reduces the average force .

How do the force–time graphs differ for a collision with and without a seat belt ?

Without a seat belt: higher peak and narrower base With a seat belt: lower peak and wider base

Wearing a seat belt gives a .......... collision time and a lower maximum force.

Wearing a seat belt gives a longer collision time and a lower maximum force.

True or False? A lower peak force on a force–time graph means a smaller impulse.

False. The impulse depends on both the force and the time . A lower peak acting over a longer time can give the same impulse.

What does an area below the time axis on a force–time graph represent?

A negative impulse . Subtract this area from the area above the axis to find the total impulse.

How can a momentum–time graph be plotted from a force–time graph?

Split the force–time graph into sections Calculate the area (impulse, or change in momentum) of each section Plot the values of momentum in each time interval

How can a force–time graph be plotted from a momentum–time graph?

Split the momentum–time graph into sections Calculate the slope (force) of each section Plot the values of force in each time interval

AP®PhysicsCollege BoardPhysics 1: Algebra-BasedFlashcardsUnit 4: Linear MomentumLinear Momentum & Impulse

Linear Momentum & Impulse (College Board AP® Physics 1: Algebra-Based): Flashcards

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FrontLinear Momentum
Define linear momentum.
FrontLinear Momentum
State the equation for linear momentum.
BackLinear Momentum
$\vec{p} = m \vec{v}$
$\vec{p}$ = momentum (kg·m/s or N·s)
$m$ = inertial mass (kg)
$\vec{v}$ = velocity (m/s)

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Cards in this collection (34)

Define linear momentum.
Linear momentum is the product of an object's mass and its velocity.
State the equation for linear momentum.
$\vec{p} = m \vec{v}$
- $\vec{p}$ = momentum (kg·m/s or N·s)
- $m$ = inertial mass (kg)
- $\vec{v}$ = velocity (m/s)
Is momentum a scalar or a vector quantity?
Momentum is a vector quantity, so it has both magnitude and direction.
Momentum has the same direction as the object's ...........
Momentum has the same direction as the object's velocity.
How does momentum differ from inertia?
- Momentum changes if the object's mass or velocity changes
- Inertia changes only if the object's mass changes
- An object at rest has inertia but zero momentum
True or False?
Two objects with different masses can have the same momentum.
True.
A light object moving fast can have the same momentum as a heavy object moving slowly, because momentum depends on both mass and velocity.
State Newton's second law in terms of momentum.
The rate of change of momentum is equal to the net external force exerted on an object (or system).
State the equation for net force in terms of momentum.
${\vec{F}}_{net} = \frac{∆ \vec{p}}{∆ t}$
- ${\vec{F}}_{net}$ = net external force (N)
- $∆ \vec{p}$ = change in momentum (kg·m/s)
- $∆ t$ = time interval (s)
State the equation for change in momentum.
$∆ \vec{p} = \vec{p} - {\vec{p}}_{0}$
- $∆ \vec{p}$ = change in momentum (kg·m/s)
- $\vec{p}$ = final momentum (kg·m/s)
- ${\vec{p}}_{0}$ = initial momentum (kg·m/s)
The equation ${\vec{F}}_{net} = \frac{∆ \vec{p}}{∆ t}$ can be used even when the .......... of the body is not constant.
The equation ${\vec{F}}_{net} = \frac{∆ \vec{p}}{∆ t}$ can be used even when the mass of the body is not constant.
How does the momentum form of Newton's second law simplify when the mass is constant?
${\vec{F}}_{net} = \frac{m ∆ \vec{v}}{∆ t} = m \vec{a}$
True or False?
An object that rebounds at the same speed has zero change in momentum.
False.
The velocity reverses direction, so the momentum reverses too. The change in momentum has magnitude $2 m v$ .
Define impulse.
Impulse is the product of the average force exerted on an object and the time interval over which the force acts.
State the equation for impulse.
$\vec{J} = {\vec{F}}_{avg} ∆ t$
- $\vec{J}$ = impulse (N·s)
- ${\vec{F}}_{avg}$ = average force (N)
- $∆ t$ = time interval over which the force acts (s)
Is impulse a scalar or a vector quantity?
Impulse is a vector quantity, so it has both magnitude and direction.
Impulse has the same direction as the .......... force exerted on the system.
Impulse has the same direction as the net force exerted on the system.
How do seat belts and airbags reduce the force on a passenger in a collision?
They increase the collision time. The impulse is constant, so the average force decreases.
Why does a crumple zone reduce the force on a passenger?
It increases the distance over which the car's kinetic energy is dissipated. By the work-energy theorem, $∆ K = W = F d$ , so a larger distance means a smaller force.
True or False?
Impulse and force are equivalent quantities.
False.
Impulse is the effect of a force acting over a time interval, so it is measured in N·s, not N.
What is 1 N·s in SI base units?
$1 N·s = 1 {kg·m/s}^{2} \times 1 s = 1 kg·m/s$
These are the same units as momentum.
State the impulse–momentum theorem.
The impulse exerted on a system is equal to the change in momentum of the system.
State the impulse–momentum theorem as an equation in terms of mass and velocity.
$\vec{J} = {\vec{F}}_{avg} ∆ t = ∆ \vec{p} = m (\vec{v} - {\vec{v}}_{0})$
- $\vec{J}$ = impulse (N·s)
- ${\vec{F}}_{avg}$ = average force (N)
- $∆ t$ = time interval (s)
- $m$ = mass (kg)
- $\vec{v}$ = final velocity (m/s)
- ${\vec{v}}_{0}$ = initial velocity (m/s)
How does Newton's second law follow from the theorem?
For a system of constant mass:
${\vec{F}}_{net} = \frac{∆ \vec{p}}{∆ t} = m \frac{∆ \vec{v}}{∆ t} = m \vec{a}$
For a given change in momentum, a small force acting over a .......... time has the same effect as a large force acting over a short time.
For a given change in momentum, a small force acting over a long time has the same effect as a large force acting over a short time.
True or False?
A crumple zone reduces the change in momentum of a car in a crash.
False.
The change in momentum is the same with or without a crumple zone. The crumple zone increases the collision time, which reduces the average force.
A rubber ball bounces off a wall at the same speed it hit it. An identical clay ball sticks to the wall. Compare the impulses delivered.
The impulse on the rubber ball is twice the impulse on the clay ball.
- Rubber ball: $∆ p = - m v - m v = - 2 m v$
- Clay ball: $∆ p = 0 - m v = - m v$
What does the area under a force–time graph represent?
Impulse, which is equal to the change in momentum.
$area = {\vec{F}}_{avg} ∆ t = \vec{J} = ∆ \vec{p}$
What does the slope of a momentum–time graph represent?
The net external force exerted on the system.
$slope = \frac{∆ \vec{p}}{∆ t} = {\vec{F}}_{net}$
How do the force–time graphs differ for a collision with and without a seat belt?
- Without a seat belt: higher peak and narrower base
- With a seat belt: lower peak and wider base
Wearing a seat belt gives a .......... collision time and a lower maximum force.
Wearing a seat belt gives a longer collision time and a lower maximum force.
True or False?
A lower peak force on a force–time graph means a smaller impulse.
False.
The impulse depends on both the force and the time. A lower peak acting over a longer time can give the same impulse.
What does an area below the time axis on a force–time graph represent?
A negative impulse. Subtract this area from the area above the axis to find the total impulse.
How can a momentum–time graph be plotted from a force–time graph?
- Split the force–time graph into sections
- Calculate the area (impulse, or change in momentum) of each section
- Plot the values of momentum in each time interval
How can a force–time graph be plotted from a momentum–time graph?
- Split the momentum–time graph into sections
- Calculate the slope (force) of each section
- Plot the values of force in each time interval

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