# AP Physics 1: 3.3 Object Interaction and Forces

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

AP Physics 1 | Object Interaction and Forces |

Language | English Language |

### Transcript

maintain in order for the box to remain attached to

the van and hear the potential answers all about friction

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

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

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

got one force the van going in the ex direction

And this question will label that in for normal force

to calculate that force we use our trusty formula force

equals mass times acceleration Then we have to force is

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

box and friction pushing it up In order for the

box to not fall these two forces have to balance

each other out So the force along the y axis

is equal to mass times gravity plus friction Well because

the forces air acting in different directions the first part

of the equation mass times gravity will be expressed as

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

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

The normal force in is pushing back Against the box

the normal force and the coefficient of friction together create

the friction force Here The equation is friction is less

than or equal to the coefficient of friction times the

normal force in the equation musa bass represents the coefficient

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

is asking us to find the minimum acceleration needed to

hold the box in place If the normal force is

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

balance out gravity in the box and fall But if

gertrud floors it jacking the normal force way up a

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

be pushing on the box so hard that the friction

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

the equation has a lesser than or equal to sign

since we need to find the minimum force needed for

gertrude to make this crazy scheme work that means that

friction force needs to be at its highest possible point

Thor equation for four should really have an equal sign

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

the uae direction the equation to use is force equals

the product of negative mass and gravity plus the product

of the coefficient of friction and the normal force And

normal force equals mass times acceleration Lastly the result of

our equation is zero because the forces balance each other

out right When we simplify the equation and solve for

acceleration we see that acceleration equals gravity divided by the

coefficient of friction for ten meters per second squared divided

by zero point six which comes out to about sixteen

point seven meters per second squared making option D The

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