# Force Body Diagram Hamster-

## Homework Statement

A 200 g hamster sits on an 800 g wedge shaped block. The block, in turn rests on a spring scale.

a) Initially static friction is sufficient to keep the hamster from moving. In this case the hamster and the block are effectively a single 1000g mass and the scale should read 9.8 N. Show that this is the case by treating the hamster and the block as separate objects and analyzing the forces.

## The Attempt at a Solution

I am reviewing, and I know I did this problem correctly before, but now it's not working for me. Could someone please tell me what I am doing wrong

Hamster: I drew a force body diagram, tilting the x & y axes

Sum of forces on y = Force of Block on hamster - mgcos40=0

Force of block on hamster = (.200kg)(9.80)(cos40)

Block: For the block I didn't tilt the coordinates

Sum of forces on y= normal force - Force of hamster on block in y direction - Mg
= n - (.200kg)(9.80)(cos40)(cos40) - (.800kg)(9.80)
n= -8.99 N which is the answer for the second part of the question, when the static friction goes away.

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tiny-tim
Homework Helper
Hi bcjochim07! You're not asked for the separate friction force at this stage, so just calculate R, the total reaction force (normal + friction).

That makes only two forces on the hamster … R and mg.

So R = … ?

Then use minus R for the block. Ok I got it, I forgot that friction has an equal opposite force