# Minimum Acceleration for Sliding Cream Pie: Solving Static Friction Problem

• Jericho_15
In summary, the coefficient of static friction between your hand and a pie is 0.70. If you want to put a cream pie pie in someone's face, what is the minimum acceleration needed to keep it from sliding down your vertical hand?
Jericho_15

## Homework Statement

The coefficient of static friction between your hand and a pie is 0.70. if you want to put a cream pie pie in someone's face, what is the minimum acceleration needed to keep it from sliding down your vertical hand?

## The Attempt at a Solution

Im not sure how to go about this.. but I am prttty sure that is related to F=ma..
Help would be greatly appreciated, thanks alot..

draw a free body diagram of the PIE-mass, what forces acting downwards what forceas acting upwards? what force is the hand "pushing the" pie-what is the normal force?

ok.. i know the normal force is acting upwards, and weight is acting downwards, and there is also the force of the hand pushing on the pie.. but they don't give me a mass fro the pie.. so wouldn't that mean the normal froce and the wight cancel each other..

1)Normal force= perpendicular to the surface(the hand) look at this in this way:
hand pushes on Pie, Pie pushes same force on hand(third law of...)=Normal force direction=Left.
2)upwards-friction. moment before it slides fs=Us * N
N=normal force=(this is the key for the problem, try to figure out by your own).
Write forces in the Y direction, and in equilibrium Fy=0

Good Luck!

P.S
Mass of Pie will cancel out
and the solution is for vertical hand:
|=hand
X=Pie
_
X|
X|
X|

Last edited:
Don't forget to experimentally verify the result of the calculation.

ok, i think I am starting to figure it out... you have to take Us/g and that equals Fs

"Don't forget to experimentally verify the result of the calculation."
xD I would've preferred eating the pie :D
You're close to the answer :}
btw there was a mistake in my last post
i wrote fs=us*m*n , its us*N

I'm off now, good luck solving, other ppl can help you for now :
good luck.

Last edited:
Fs= Us * M*N
Fs= Us *M/mg
Fs=Us/g
Fs=.0713

no i take the Fs and plug it back in right
so now i do this:
Fs=Us*n
Fs/Us=n
.0713/.70=.101
n=.101
so that would mean since N=.101
acceleration is also equal .101n

Last edited:
Is anyone elsehere that can help me..

check my last post.
fs=us*N.
N=m*a.
What You've done is wrong Imo.

ok if what ur saying is true, then that would mean Fs and Us are equal, and my acceleration would be 1.. but i think that wouldn't make sense... corret me if I am wrong.

I really wonna sleep xD
fs=static friction=MG(in equilibrium state)=us*N
how did yo get that they're equal (fs and us).

Hope You see this:
mg down, friction up which depends on the normal force, normal force acting on hand (and by hand on body).
good luck.

i still can't get it... anyone else can help me cause I am stuck...

## What is static friction?

Static friction is a type of force that acts in the opposite direction to the applied force, preventing an object from moving when a force is applied to it. It is the force that keeps an object at rest on a surface.

## Why is static friction important?

Static friction is important because it allows objects to stay in place without sliding or moving when a force is applied to them. This helps to maintain stability and prevent accidents.

## What factors affect static friction?

The amount of static friction between two surfaces depends on the nature of the surfaces, the force applied, and the coefficient of static friction, which is a measure of the roughness of the surfaces in contact.

## How do you calculate static friction?

The formula for calculating static friction is: Fs ≤ μsN, where Fs is the force of static friction, μs is the coefficient of static friction, and N is the normal force between the two surfaces.

## What is the difference between static and kinetic friction?

Static friction acts on stationary objects, while kinetic friction acts on objects in motion. Static friction is typically stronger than kinetic friction, as it takes more force to overcome the initial resistance and start an object moving.

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