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AP Physics 1: 3.3 Object Interaction and Forces 174 Views


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AP Physics 1: 3.3 Object Interaction and Forces. What is the minimum acceleration needed for the box to remain attached to the van?

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Transcript

00:00

Thank you We sneak and here's your shmoop du jour

00:05

brought to you by vans which just aren't as groovy

00:08

as they used to be Check the falling image and

00:12

passage Nice hair glasses in your stuff All right What

00:20

is the minimum acceleration that aunt gertrude would have to

00:23

maintain in order for the box to remain attached to

00:26

the van and hear the potential answers all about friction

00:30

Uh no There's A lot going on in this question

00:33

Well let's try to make it simpler on ourselves by

00:35

drawn up the little force diagram right here Okay we've

00:40

got one force the van going in the ex direction

00:43

And this question will label that in for normal force

00:47

to calculate that force we use our trusty formula force

00:50

equals mass times acceleration Then we have to force is

00:53

in the y direction there's gravity pulling down on the

00:56

box and friction pushing it up In order for the

00:59

box to not fall these two forces have to balance

01:02

each other out So the force along the y axis

01:05

is equal to mass times gravity plus friction Well because

01:09

the forces air acting in different directions the first part

01:12

of the equation mass times gravity will be expressed as

01:16

a negative number and here's the equation All right Well

01:19

now let's deal with the friction in our scenario here

01:22

The normal force in is pushing back Against the box

01:25

the normal force and the coefficient of friction together create

01:28

the friction force Here The equation is friction is less

01:32

than or equal to the coefficient of friction times the

01:36

normal force in the equation musa bass represents the coefficient

01:41

of static friction it's important to remember that the question

01:45

is asking us to find the minimum acceleration needed to

01:48

hold the box in place If the normal force is

01:51

too small the friction force won't be strong enough to

01:53

balance out gravity in the box and fall But if

01:56

gertrud floors it jacking the normal force way up a

02:00

friction force will reduce that's because the normal course would

02:03

be pushing on the box so hard that the friction

02:05

force wouldn't have to be doing this much That's why

02:08

the equation has a lesser than or equal to sign

02:11

since we need to find the minimum force needed for

02:14

gertrude to make this crazy scheme work that means that

02:17

friction force needs to be at its highest possible point

02:20

Thor equation for four should really have an equal sign

02:24

okay quick reminder We're trying to balance the forces in

02:27

the uae direction the equation to use is force equals

02:31

the product of negative mass and gravity plus the product

02:35

of the coefficient of friction and the normal force And

02:38

normal force equals mass times acceleration Lastly the result of

02:43

our equation is zero because the forces balance each other

02:46

out right When we simplify the equation and solve for

02:50

acceleration we see that acceleration equals gravity divided by the

02:54

coefficient of friction for ten meters per second squared divided

02:58

by zero point six which comes out to about sixteen

03:02

point seven meters per second squared making option D The

03:06

correct answer And we're thinking of trading in our van 00:03:09.02 --> [endTime] for something easier to parallel park

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