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1. Define momentum.

2. Calculate the momentum of a moving object.

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Example 1:

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Example 2:

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DEFINITION: Momentum is the product of mass and velocity of an object. 

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DEFINITION: Momentum is the product of mass and velocity of an object. 

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Momentum = The product of the mass and velocity of an object.

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p ∝ m

p ∝ v

p = mv

UNITS:
m = kg
v = m.s⁻¹
p = kg.m.s⁻¹

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Momentum has both magnitude and direction.

It can have positive and negative values.

Negative answers must be changed to positive final value with direction.

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A car (m=2000kg) travels at 32 m.s⁻¹. What is its momentum?

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An 8kg bowling ball is rolling straight towards you. Its momentum is 16kg.m.s⁻¹. How fast is it traveling?

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1.

What is the momentum of a child and wagon if the total mass of the child and wagon is 22kg and the velocity is 1.5m/s?                       [Answer: 33kg.m/s]

2.
The parking brake on a 1200kg car has broken, and the vehicle has reached a momentum of 7800kg.m/s. What is the velocity of the vehicle? [Answer: 6.5m/s]

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NET FORCE ACTING ON A BODY CHANGES THE MOMENTUM OF THAT BODY

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NET FORCE ACTING ON A BODY CHANGES THE MOMENTUM OF THAT BODY

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Fnet.Δt  =  Δp
=  m.Δv
=  m (vf  -  vi)

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Δp = pf - pi
= mvf  -  mvi
= m (vf - vi)

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EXAMPLE 1
A 5 kg mass has its velocity changed from 8 m/s east to 2 m/s east.  Find the object’s change in momentum.

m = 5.0 kg
V i = 8.0 m/s East
V f = 2.0 m/s East
Δp = ?

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Δp = mΔV

= (5)(2 - 8)

= -30 kg.m.s⁻¹ East

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A tennis ball (mass 57 g) travels horizontally towards a wall, and strikes it at 20m/s. It rebounds horizontally at 30 m/s away from the wall.
Calculate the change in momentum of the tennis ball.
CHOOSE A +ve DIRECTION FIRST!

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Δp = mΔV
=  m(v f - v i)

= (0,057)[-30 - (+20)]

= - 2,85 kg.m.s⁻¹
= 2,85 kg.m.s⁻¹ away from the wall

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State Newton's second law in terms of momentum:
The net force acting on an object is equal to the rate of change of momentum.

(There are two acceptable statements of Newton's Second Law)

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NEWTON 2nd LAW APPLICATION IN MOMENTUM CALCULATIONS

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NEWTON 2nd LAW APPLICATION IN MOMENTUM CALCULATIONS

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Car safety:

This takes a look at how air bags and crumple zones in cars decrease the net force acting on passengers in a collision.

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0:00 / 3:11•Watch full video

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WILL THE MOMENTUM OF AN OBJECT ALWAYS INCREASE IF A NET FORCE ACTS ON IT? 

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WILL THE MOMENTUM OF AN OBJECT ALWAYS INCREASE IF A NET FORCE ACTS ON IT? 

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No.

Momentum will decrease if the net force acts in the opposite direction to motion.

E.g. friction acting on an object.

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Error 18. Please try again in a few minutes or contact support for further help. Thanks for your patience!

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Bullet stopped by water - momentum ballistics Smarter Every Day

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Easily create beautiful interactive video lessons for your students you can integrate right into your LMS. Track students' progress with hassle-free analytics as you flip your classroom!

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A System = a portion of the universe under study, with two or more objects interacting.

Isolated system = System with constant mass and no net external force.

Law of conservation of linear momentum = Total linear momentum of an isolated system remains constant (conserved).

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0:00 / 0:24•Watch full video

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Conservation of Momentum (1-D) on Air Track

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Comparing momentum before and after a collision.

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CTSC practical experiment: Conservation of momentum

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What you should know by the end of this section:

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What you should know by the end of this section:

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Momentum is the product of mass and velocity.

Momentum is a vector quantity.

Momentum is always conserved in collisions.

The law of conservation of momentum: The total linear momentum of an isolated system is conserved.

If there are no external forces acting on a system, the total linear momentum of all particles or objects in the system remains constant.

A change in momentum of objects require a change of velocity, hence it requires a force.

Solve collision problems in physics by equating the before and after momentum:   p before = p after

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What is the link between R2-D2 and science homework?

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Inelastic and Elastic Collisions: What are they?

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0:00 / 6:45•Watch full video

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Introduction to Elastic and Inelastic Collisions

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Experiment 2 - Elastic vs. inelastic collision

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Experiment 2 - Elastic vs. inelastic collision

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Solutions to Momentum Impulse Key Problems

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Impulse
 Define impulse (J) as the product of the net force and the contact time
 Solve problems using J = Fnet. t
 Know impulse is a vector and in the same direction as the net force vector
 Know that impulse and change in momentum are equivalent, i.e. J = DELTA p
 Solve problems using net delta p = F net . delta t
 Apply the concept of impulse in everyday life, e.g. airbags, catching a hard ball

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Airbags

Truck arrestor beds

Sports

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SYLLABUS