Free Body Diagram


by plshelpme
Tags: body, diagram, free
plshelpme
plshelpme is offline
#1
Feb8-09, 06:19 AM
P: 3
1.
The problem statement, all variables and given/known data

A large box containing your new computer sits on the bed of your pickup truck. You are stopped at a red light. The light turns green and you stomp on the gas and the truck accelerates. To your horror, the box starts to slide toward the back of the truck. (Assume that the truck is accelerating to the right.)

part 1)
Draw clearly labeled free-body diagram for the box
given the following vectors:
1] weight of box
2] normal force
3] box's friction force on the truck
4] unlabelled vector

part2)
Draw clearly labeled free-body diagram for the truck.
(The bed of the truck is not frictionless.)
given the following vectors:
1] reaction force to tires' backward push
2] normal force from ground
3] weight of truck
4] reaction to the normal force on the box from the truck
5] the box's friction force on the truck
6] unlabelled vector

2. Relevant equations



3. The attempt at a solution

part a attempt is

weight downwards
normal force upwards
box's friction force on the truck to the right
unlabelled vector (not sure it used as a accelerating vector of the box) to the left

part b attempt is

1] reaction force to tires' backward push - to the right
2] normal force from ground - upwards
3] weight of truck - downwards
4] reaction to the normal force on the box from the truck - upwards
5] the box's friction force on the truck - to the left
6] unlabelled vector - to the right

i am not sure of the answers...
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LowlyPion
LowlyPion is offline
#2
Feb8-09, 10:35 AM
HW Helper
P: 5,346
Quote Quote by plshelpme View Post
part a attempt is

weight downwards
normal force upwards
box's friction force on the truck to the right
unlabelled vector (not sure it used as a accelerating vector of the box) to the left

part b attempt is

1] reaction force to tires' backward push - to the right
2] normal force from ground - upwards
3] weight of truck - downwards
4] reaction to the normal force on the box from the truck - upwards
5] the box's friction force on the truck - to the left
6] unlabelled vector - to the right

i am not sure of the answers...
In Part a, your Force vector on the box = m*a the acceleration in the frame of reference of the truck bed I think.

In b) I would make the normal force = truck + box
And what is the unlabeled vector to the right? Isn't that the reaction force on the ground already? The tires are pushing a force to the left aren't they if the truck is moving right?


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