# AP Physics 1: 2.1 Changes and Conservation Laws

AP Physics 1: 2.1 Changes and Conservation Laws. What will happen to the velocity of the ball if the length of the string is halved?

AP Physics 1 | Changes and Conservation Laws |

Language | English Language |

Science Practice 3 | Engaging in scientific questioning |

### Transcript

spun with equal force what will happen to the velocity

of the ball if the length of the string is

have And here the potential answers All right equal forces

Well that's Really important Okay so let's think about angular

momenta Angular momentum is the amount of rotation object has

mathematically speaking Angular momentum is the product of mass velocity

and distance from the centre which we can think of

as the objects radius good word and the our baby

And we know once mo mentum starts it won't stop

or change until something acts to change it that's the

law of conservation of momentum That's what nunes first laws

all about an object in motion stays in motion until

something acts on it and rotating or orbiting objects have

their own law of conservation of angular momentum The idea

is the same No angular momentum doesn't change unless it

has To just like us with socks way Don't change

him unless we have to get pretty pungent by your

laundry day So if an object momentum doesn't change unless

something acts upon it well what happens if the object

itself changes We'll answer that by talking about our favorite

sport figure skating We get so hyped about the winter

olympics and every four years you start dressing like ice

dancers just to get into the spirit All right well

we especially love when a figure skater starts twirling around

and then she goes faster and faster and we get

dizzy just looking at her The reason she picks up

speed is because she changes her radius She starts spinning

with a certain momentum and she has her arms out

wide like that A speeder spin She brings her arms

and is close to her body She can decreasing her

radius Her velocity than increases that's because the angular momentum

has to remain the same and her mass isn't changing

So if one part of the equation decreases another part

has to increase So now let's take a look at

our question If the force applied to the ball is

the same that means the angular momentum has to be

the same too So if we cut the length in

half the rest of the equation has to double The

mass of the ball isn't changing so the velocity will

have to double means going to spin around twice as

fast It means the right answer is c Now we're

going to get back to our rodent tether ball match

It's super cute toe watch But sometimes steve the mouth 00:02:33.603 --> [endTime] can be a real sore loser