# Free Body Diagram, Newton's 3rd

#### myxomatosii

[SOLVED] Free Body Diagram, Newton's 3rd

SOLVED

1. Homework Statement

A 1200 kg car pushes a 2000 kg truck that has a dead battery. When the driver steps on the accelerator, the drive wheels of the car push against the ground with a force of 4700 N.

(a) What is the magnitude of the force of the car on the truck?
(b) What is the magnitude of the force of the truck on the car?

2. Homework Equations

fs=$$\mu$$sn
F=ma
Fnetc/mc=FnetT/FT

3. The Attempt at a Solution

I drew this free body diagram, I am not really sure how to set this problem up but I thought this would be a good start.

Wanted to see how "right" it is.

nc = normal force of car
nT = normal force of truck
fsc = static friction force
Fc on T = force of car on Truck
FT on c = force of Truck on car
mcg = weight of car
mTg = weight of truck

http://img27.imageshack.us/img27/8660/fbda88b.jpg [Broken]

I've done a little dabbling with formulas from there but nothing great. I haven't solved anything so.. maybe I can at least figure out if my drawing is right.

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#### sArGe99

Newton's Third Law of Motion?

#### myxomatosii

Solved! Used the materials forum on this site.

I know people google questions like these a lot, at least I do. You will find a very good lecture on this exact problem at the link I will provide, 16 minutes into Lecture 6.

http://www.free-ed.net/free-ed/Science/Physics/physicsMIT01_VOD.asp

#### sArGe99

But if you know the concept correctly, you can solve pretty much any problem based on that.

#### myxomatosii

But if you know the concept correctly, you can solve pretty much any problem based on that.
I hope so, I'm trying it out now.

To tell you the truth I've been studying these ideas for the past 7 hours and I'm becoming quite tired... so I don't know how well I can apply them at the moment. Normally I am at work right now but I called out to spend the whole night on this.

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