MT5 (Momentum and its Conservation)

Two Types of Collision: (all info)

1) Elastic: Two objects collide and bounce apart -Two objects bounce apart and have different final velocities 2) Inelastic: Two objects collide and stick together -The two objects stick together and have the same final velocity

also know ice skater information and practice problems in notebook

:)

What is angular momentum?

A rotating object of product of its momentum of inertia and angular velocity

momentum is measured in

Kg-m/s

impulse is measured in

N

How does Newton's third law relate to conservation of momentum?

Newton's third law states that for a force applied by an object A on object B, object B exerts back an equal force in magnitude, but opposite in direction. This idea was used by Newton to derive the law of conservation of momentum. In other words, the momentum of an isolated system will always remain the same.

Under which conditions is momentum conserved?

States that in a closed isolated system it is conserved.

How can the law of conservation of momentum and the law of conservation of angular momentum help explain the motion of objects?

When an object is spinning in a closed system and no external torques are applied to it, it willhave no change in angular momentum. The conservation of angular momentum explains the angular acceleration of an ice skater as she brings her arms and legs close to the vertical axis of rotation.

The angular velocity of an object can change, however, even if no torques are acting on it. This is because the moment of inertia depends on the object's mass and the way it is distributed about the axis of rotation. For example, _______________________________________.

a diver can control her angular velocity by changing her moment of inertia

Give three examples of when he gyroscope effect is used. (See page 253.)

airplanes, submarines, and spacecraft

What is the difference between a closed system and an isolated system?

an isolated system is when the net force on a closed system is zero

Linear momentum is the product of the moment of inertia and angular velocity for a rotating object.

angular

The ____ states that the angular impulse on an object equals the difference in the object's final and initial angular momenta.

angular impulse-angular momentum theorem

If there are no torques acting on an object, its _______________ is constant.

angular momentum

Like linear momentum, ______________ can be conserved under certain conditions.

angular momentum

The product of a rotating object's moment of inertia and its angular velocity is the ____ of the object.

angular momentum

The _______________ of an object can change, however, even if no torques are acting on it.

angular velocity

impulse size is the

area under the graph

A system which does not gain or lose mass is said to be a _____________.

closed system

A(n) ___ is a system that does not gain or lose mass.

closed system

In a(n) ____ , mass in neither gained nor lost.

closed system

A rocket and its fuel form a _________________.

closed, isolated system

In a _______________, momentum is transferred between objects

collision

You can use this law to relate ___ before and after an interaction even if you do not know any details of the ___.

conditions; interaction

As each planet orbits the Sun, its angular momentum is zero because the torque on each planet is zero.

constant

2 types of collision

elastic and inelastic

Forces that are outside this system are ___.

external force

A gyroscope is a wheel or disk that spins rapidly around two or more axes.

false

By moving her arms outward, an ice skater speeds up a spin, while moving her arms inward slows down a spin.

false

The angular impulse on an object is equal to the object's initial angular momentum minus the object's final angular momentum.

false

The law of conservation of angular momentum states that if no external force acts on an object, then its angular momentum does not change.

false

A planet moves slower when its distance from the Sun decreases.

faster

When the fuel and oxidizer combine in a rocket motor, the resulting hot gases leave the exhaust nozzle at high speed. By the law of conservation of momentum and Newton's third law of motion, this results in the rocket being propelled ___________.

forward

The momentum of the system after the push is ___.

greater than zero

A _____________ is a wheel or disk that spins rapidly around one axis while being free to rotate around one or two other axes.

gyroscope

The ____________ on an object is the product of the average force on an object and the time interval over which it acts.

impulse

The product of the average force on an object and the time interval over which it acts is ____.

impulse

The ____ states that the impulse on an object is equal to the change in the object's momentum.

impulse-momentum theorem

As an ice skater spins and pulls her arms closer to her body, her angular velocity decreases because of the change in her moment of inertia.

increases

What is momentum?

inertia in motion

Within such a system, all forces are ___.

internal force

In a(n) ____ , no net external force is exerted on the system.

isolated system

This system is a(n) ___ when the net external force on it is zero.

isolated system

When the net external force on a closed system is zero, the system is described as an ________________.

isolated system

What if the mass of a particle were to suddenly drop to zero? According to the information in chapter 9, what would happen to the momentum of the particle?

it would also be zero

State the units for angular momentum.

kg-m2/S

The ____ states that an object's initial angular momentum equals its final angular momentum when no external torque acts on the object.

law of conservation angular momentum

The ____ states that the momentum of any closed, isolated system does not change.

law of conservation of momentum

The ________________________: the momentum of any closed, isolated system does not change.

law of conservation of momentum

The ___ states that the momentum of the system does not ___ if the system has no net external forces acting on it.

law of conservation of momentum; changed

The momentum of the first skater after the collision is ___, and that of the second skater is ___.

less than zero; greater than zero

If there are no forces acting on an object, its ____________ is constant.

linear momentum

The angular velocity of an object can change, however, even if no torques are acting on it. This is because the moment of inertia depends on the object's___________ and the way it is distributed about the ______________.

mass --- axis of rotation

List two ways in which impulse can be increased.

mass and velocity

The product of the object's mass and the object's velocity is defined as the ______________ of the object.

momentum

When mass is multiplied by velocity, the answer is a measure of ____.

momentum

Impulse is measured in _____________.

newton-seconds

The law of conservation of angular momentum states that if ____________ acts on an object, then its angular momentum does not change.

no net external torque

momentum formula:

p=mv

A newer type of space propulsion uses the __________ that results from the force of ions to move a spaceship.

recoil

Conservation of momentum can be used to explain _________.

recoil

backwards motion after push

recoil

the sum of momentum is the

same before and after the collision

Example of recoil:

skaters push other skater and they both move in opposite directions

How does an air bag reduce injuries that would be caused by the steering wheel during an accident? Write your answer in terms of impulse.

the air bag increases the amount of time the force of the wheel acts on the driver. the impulse doesn't chance causing the force on the driver to be reduced

What is impulse?

the change in momentum resulting from a force, measured as the product of force and time

State the impulse-momentum theorem.

the impulse on an object is equal to the change in its momentum

If the top is _________, as shown in the figure, a torque tries to rotate it downward. Rather than tipping over, however, the upper end of the top revolves, or precesses slowly about the vertical axis.

tipped

A net torque on an object results in a change in angular momentum.

true

An object's moment of inertia depends upon the distribution of mass about the axis of rotation.

true

Net force changes momentum, while net torque changes angular momentum.

true

The law of conservation of momentum states that the momentum of a closed, isolated system does not change.

true

The moment of inertia around a given axis of a fixed, solid object cannot be changed.

true

When there is no torque acting on a body, its angular momentum is constant.

true

Momentum is ______________ (it has direction).

vector quantity

Because an object's mass cannot be changed, if its momentum is constant, then its _____________ is also constant.

velocity

When a top is __________, there is no torque on it, and the direction of its rotation does not change.

vertical

The total momentum of the system was zero before the push, so it must be _________ after the push.

zero

Two in-line skaters are standing still on a surface that is smooth so that there are no external forces. The first skater gives the second skater a push in one particular direction. The momentum of the system before the push is ___.

zero

elastic collision

•Two objects collide and bounce apart --Two objects bounce apart and have different final velocities

inelastic collision

•Two objects collide and stick together --The two objects stick together and have the same final velocity