«Сақталу заңдары» Механикадағы импульс пен энергияның сақталу заңдары және олардың кеңістік пен уақыттың қасиеттерімен байланысы. Физика, 10 сынып, презентация.

HARD TO STOP

Why can’t it stop easily ??

1. It is MASSIVE

2. It is FAST

IT has a lot of MOMENTUM

MOMENTUM

MOMENTUM

=

MASS

X

VELOCITY

p = m v

UNITS of MOMENTUM

Mass x velocity = kg x m s-1 = kg ms-1

But the preferred unit of Momentum is N s

NEWTON SECONDS

m = 150 000 tonnes

QM2

Ferrari F1

v = 25 knots = 12.5 m s-1

p = ?

150 000 000 kg x 12.5 ms-1

= 1875 000 000 kg ms-1

= 1.875 x 109 N s

m = 650 kg

v = 200 mph = 89 m s-1

p = ?

650 kg x 89 ms-1= 57 850 kg ms-1

= 5.785 x 104 N s

THE PRINCIPLE OF CONSERVATION OF MOMENTUM

THE TOTAL MOMENTUM OF A SYSTEM

IS CONSTANT,

PROVIDING THAT NO EXTERNAL FORCES ARE ACTING ON IT

This principle applies to collisions and to explosions

THE PRINCIPLE OF CONSERVATION OF MOMENTUM

so

m1

BEFORE

m2

AFTER

m1u1 + m2u2 =

m1v1 + m2v2

REMEMBER THAT MOMENTUM IS A VECTOR QUANTITY

VECTOR QUANTITY

VECTOR QUANTITY

VECTOR QUANTITY

VECTOR QUANTITY

v = ?

BANG !

MOMENTUM BEFORE

=

MOMENTUM AFTER

By the Principle of Conservation of Momentum

(2 x 2) + (4 x (-4)) = 2 x (-2.5) + 4 v

4 - 16 = -5 + 4 v

v = - 1.75 m s-1

Note that the 4 kg ball was moving to the left initially

THE PRINCIPLE OF CONSERVATION OF MOMENTUM

This principle applies to collisions and to explosions

By the Principle of Conservation of Momentum

Taking to the right as positive

0 = - m v + M V

After it has fired the shell, the initial recoil velocity of the tank is given by

m = mass of shell

M = mass of tank

Momentum = 0

ELASTIC AND INELEASTIC COLLISIONS

MOMENTUM IS CONSERVED IN ALL COLLISIONS

KINETIC ENERGY IS ONLY CONSERVED FOR ELASTIC COLLISIONS

FOR EXAMPLE COLLISIONS BETWEEN ATOMS OF A MONOATOMIC GAS