# AP Physics 1: 2.2 System Interactions and Changes

AP Physics 1: 2.2 System Interactions and Changes. What is the velocity of the stone at 12 seconds?

AP Physics 1 | System Interactions and Changes |

Language | English Language |

Science Practice 5 | Performing data analysis |

### Transcript

show that tests the physics knowledge of random passers by

The host shows ernie the force time diagram above which

is based on the motion of a two kilogram stone

that rules across ah horizontal surface He asks what is

the velocity of the stone at twelve seconds and hear

potential answers Yeah all right well let's look at our

diagram here We're dealing with a force time diagram Anytime

we see force in time together like this we know

we're dealing with impulse Impulse equals force applied over an

interval of time and impulses equal toe linear momentum and

momentum Well it's the product of mass and velocity Right

To find the total impulse in a diagram like this

we need to calculate the area under the curve right

there We can make that easier by breaking the diagram

into two triangles and a rectangle like this Now we

only need the area for the first triangle and the

rectangle Since we need to know the velocity at twelve

seconds we could do a little old school geometry to

figure those out The area of the triangle is twenty

In the area of the rectangle is sixty giving us

a total impulse of lady Well now we can just

put the numbers we have into the equation in salt

for velocity with the impulse which is eighty equals two

kilograms times velocity When we do the math we see

that the velocity is forty meters per second making option

b the correct answer Just to be safe we'll be

sure to remember how to figure out impulse in case

wherever ambushed on the street by some physics crazed game 00:02:02.69 --> [endTime] show