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zell_D

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## Homework Statement

A sled weighing 60 N is pulled horizontally across snow so that the coefficient of kinetic friction between sled and snow is .100. A penguin of 70 N rides on the sled

a) The penguin digs claws into sled, what value of F do you need for the sled and penguin to move at constant speed

b) The penguin releases grip on the sled, coefficient of static friction between penguin and sled is .700, find the maximum horizontal force F that can be exerted on the sled before the penguin starts sliding off

## Homework Equations

F=ma

Newton's 2nd and 3rd? law

## The Attempt at a Solution

a) constant speed implied a=0

F=ma -> F=0

FN=Fg, FN=mg

Fapplied=friction

Fapplied=(.100)FN=.100*(60+70)=13N to move at constant speed

b) actually only 3 forces acting on the penguin FN Fg static friction

static friction = .700*mg

=.700(70)=49 N = max static friction threshold. So a force that's > 49 N needs to be exerted on the slide before the penguin falls off?

I am assuming kinetic friction has no role in this problem and that since acceleration is not asked for I don't have to set 49 to ma to find the max acceleration before it slides off and everything.