Laws or motions and a truck that won't move.

• azertyq
In summary, the speaker has been struggling with a problem that has been taking up a lot of their time. They are trying to find the force in the members of a towing crane, given that a tow truck is pulling on a car with a 2500N force. They provide their calculations and results, but later realize they made a computational error and the correct values for Fa and Fb are 3.83kN and 3.37kN. They apologize for bothering anyone and acknowledge that mistakes happen.
azertyq
I have been bothered with a problem that I know should not be monopolizing as much time as it has. It just annoys me how I keep missing the little thing that would make the problem more understandable.

Anyways, here is the problem, with my attempt of a solution:

a tow truck pulls on a car with a 2500N force directed along the cable used for towing. The purpose of the problem is to find the force in the members of the 'towing crane' used, assuming that both the car and the truck are not moving. (the attached FBD should make more sense.. sorry)

Here are the calculations and results I got:

(sum of forces F) F = ma = 0 // at the point C where the three forces are joined

--> Fx= 0 and Fy=0

F1= -2500* cos(40) i - 2500*sin(40) j // finding the vector corresponding to each force

Fa= - Fa j

Fb= Fb*cos(50) i - Fb*sin(50) j

Fx= [ (-2500* cos(30) + Fb*cos(50)]= 0 //applying the equilibrium equation
--> Fb = 2500* cos(30) / *cos(50)
Fb= 1632 N
Fy= [ - 2500*sin(30) - Fa - Fb*sin(50)] = 0

--> Fa = -(2500*sin(30) + Fb*sin(50))
Fa = -(2500*sin(30) + 2979*sin(50))
Fa= 3214 N

It seems logic to me that it'd be the correct resolution path, but according to the textbook, the correct values for Fa and Fb are

Fa= 3.83kN and Fb=3.37kN

Quite different from what I got indeed.

If anyone could help me with this problem, it'd be great. I tried. I really did. :(

Attachments

• physics.JPG
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I feel kind of stupid after finding out that I had jut made a computation error.
I guess things like that are bound to happen. >_<
lol

Sorry to have bothered you guys.

Thank you for sharing your problem and your attempted solution. It can be frustrating when we put in effort to solve a problem and still come up with incorrect results. In this case, it seems like there may be a mistake in your calculations or assumptions. It is always a good idea to double check your work and make sure you are using the correct formulas and units.

In terms of laws or motions, there are several principles that can help us understand why the truck is not moving in this scenario. One is Newton's First Law of Motion, which states that an object at rest will remain at rest unless acted upon by an external force. In this case, the truck is not moving because the forces acting on it are balanced, resulting in a net force of zero.

Another relevant concept is equilibrium, which is when all forces acting on an object are balanced and there is no net force. In your solution, you correctly identified that the sum of forces in the x and y directions should be equal to zero for equilibrium to be achieved. However, it is possible that there was a mistake in your calculations that led to the incorrect values for Fa and Fb.

In the end, it is important to remember that mistakes and challenges are a normal part of problem-solving. It may be helpful to go back and review the problem, check your calculations, and seek help from a teacher or classmate if needed. Keep persevering and you will eventually find the solution.

1. Why won't my truck move?

There could be several reasons why your truck won't move. It could be due to a mechanical issue such as a broken transmission or a faulty engine. It could also be caused by a lack of fuel or a dead battery. Additionally, the truck may be stuck in mud or snow, or the parking brake may be engaged.

2. What is the difference between a law and a motion?

A law is a rule or principle that governs the behavior of a system, while a motion refers to the movement or change in position of an object. Laws, such as Newton's Laws of Motion, help explain the causes of motion.

3. How do laws and motions affect the movement of a truck?

The laws of physics, specifically Newton's Laws of Motion, dictate how a truck moves. These laws state that an object will remain at rest or in a state of uniform motion unless acted upon by an external force. The truck's engine provides the necessary force to overcome the friction and resistance and propel the truck forward.

4. Can laws and motions be used to troubleshoot a truck that won't move?

Yes, understanding the laws and principles of motion can help troubleshoot issues with a truck that won't move. For example, if the truck is not accelerating as it should, it may be due to a problem with the engine or transmission, which can be addressed by applying the laws of motion.

5. How can I fix a truck that won't move due to mechanical issues?

If the truck won't move due to mechanical issues, it is best to consult a professional mechanic. They will be able to diagnose the problem and provide the necessary repairs or replacements. It is important to address any mechanical issues promptly to ensure the safe and proper functioning of the truck.

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