Free Body Diagram for a truck

In summary, the conversation discussed drawing clearly labeled free-body diagrams for a box on the bed of a pickup truck and for the truck itself. The forces included in the diagrams were weight, normal force, friction force, reaction force to tires' backward push, reaction to the normal force on the box, and an unlabelled vector. The correct labeling and direction of these forces were uncertain, but it was suggested to make the normal force on the truck equal to the sum of the normal forces on the truck and the box.
  • #1
plshelpme
3
0
1.
Homework Statement

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

Homework Equations





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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  • #2
plshelpme said:
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?
 
  • #3


I would like to provide some clarifications to the free body diagrams for the truck and the box in this scenario. Firstly, the unlabelled vector in both diagrams could potentially be the acceleration vector of the truck and the box, respectively. This is because the truck and the box are accelerating to the right, and according to Newton's second law, there must be a net force acting on them in that direction.

For the box, the free body diagram would include the weight of the box acting downwards, the normal force from the truck acting upwards, and the box's friction force on the truck acting to the right. The unlabelled vector would represent the acceleration of the box to the right.

For the truck, the free body diagram would include the reaction force to the tires' backward push, which is the driving force that causes the truck to accelerate to the right. The normal force from the ground acts upwards to support the weight of the truck, and the weight of the truck acts downwards. Additionally, there would be a reaction force to the normal force on the box from the truck, which acts downwards to counteract the normal force from the box. The box's friction force on the truck acts to the left, and the unlabelled vector represents the acceleration of the truck to the right.

It is important to note that the bed of the truck is not frictionless, so the box's friction force on the truck is necessary to prevent it from sliding off. Without this force, the box would continue to slide to the back of the truck even when the truck is not accelerating.

Overall, the free body diagrams accurately represent the forces acting on the truck and the box in this scenario. It is important to consider all the forces, including reaction forces and friction forces, to fully understand the motion of these objects.
 

1. What is a free body diagram for a truck?

A free body diagram for a truck is a visual representation of all the forces acting on the truck. It helps to analyze the motion of the truck and understand the forces that are causing that motion.

2. How do you draw a free body diagram for a truck?

To draw a free body diagram for a truck, you first need to identify all the forces acting on the truck, including gravity, normal force, friction, and applied forces. Then, draw a simple diagram of the truck and label each force with an arrow showing its direction and magnitude.

3. Why is a free body diagram important for a truck?

A free body diagram is important for a truck because it allows us to understand the forces that are acting on the truck and how they contribute to its motion. This information is crucial for designing and optimizing the truck's performance and ensuring its safety.

4. What are some common forces shown in a free body diagram for a truck?

Some common forces shown in a free body diagram for a truck include the weight of the truck, the normal force from the ground, the force of friction, and any applied forces such as engine force or air resistance.

5. How can a free body diagram for a truck be used to solve problems?

A free body diagram for a truck can be used to solve problems by applying Newton's laws of motion and using the information about the forces to calculate the acceleration and motion of the truck. This can help in determining the truck's speed, stopping distance, and other important factors related to its performance.

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