# How Should Forces Be Calculated in a Truck-Trailer System?

• MaxKempar
In summary, the total force required to pull both the truck and trailer is 35500*0.78 N. The force on the truck (f1) is calculated by multiplying the truck's mass (m1) by the acceleration (a) and is equal to 27000*0.78 N. The force on the trailer (f2) is equal to the tension force (T) and can be calculated using the formula f2 = m2a = T = 8500*0.78 N. The overall tension force in the chain holding the truck and trailer together is also equal to f2. It is not necessary to calculate f1 using the formula F = f1+f2 since it is simpler to
MaxKempar
I have a truck (m1,27000 kg) pulling a trailer (m2, 8500 kg) with a chain holding the two together (T). The overall acceleration is 0.78 m/s^2.
Find f1 force on the truck, f2 force on the trailer and T, tension force.

Here is what I did: since the force comes all from the truck, f1 = (m1+m2)(a) = 35500*0.78 N
T = -f2 = 8500 * 0.78 N

But apparently this is how you do it:

f2 = m2a=T = 27000*.78 N = T
f1 = m1a = F-T
F = f1+f2 = (m1+m2)a = 35500*.78
f1 = 35500*.78 - 27000*.78;

I just don't understand how f2 which is just being pulled can have force greater than f1 which is doing all the work.

What am I doing wrong?

Thank you

The main thing that I don't understand is F = f1+f2, how can a powerless trailer have a positive force. Wouldn't F = f1-f2?

MaxKempar said:
Find f1 force on the truck,
This part is a bit unclear, the force on the truck from where? Is it the total force or the force from the ground on the truck or the force from the chain on the truck?

+1

Find f1 force on the truck, f2 force on the trailer and T, tension force.

Do you have a diagram showing where f1 and f2 are measured?

As far as I can see these could all be the same. The chain is pulling the trailer so the tension _is_ the "f2 force on the trailer". The force f1 on the truck could be the tension in the chain or the friction force with the ground??

But apparently this is how you do it

f2 = m2a=T = 27000*.78 N = T

That's not consistent with the problem statement (m2 is 8500kg not 27000kg). It should be...

f2 = m2a = 8500 * 0.78 = T = 6630N .......(1)

f1 = m1a = F-T

That implies f1 is the force required to accelerate the truck alone without the trailer. That's OK.

F = f1+f2 = (m1+m2)a = 35500*.78

Ok so F is the total force required to bull both truck and trailer. That's OK

f1 = 35500*.78 - 27000*.78;

That doesn't make sense due to the error above at (1). Should be

f1 = 35500*.78 - 8500*.78

but there is a much easier way to calculate f1...

f1 = m1*a = 27000 * 0.78

I don't see why they need to make it so complicated.

## What is truck pulling trailer?

Truck pulling trailer refers to the practice of using a truck to pull a trailer, which is a wheeled vehicle that is designed to be towed by a motor vehicle. This is a common method of transporting goods and materials, especially for large and heavy items.

## What are the different types of trailers used for truck pulling?

There are various types of trailers used for truck pulling, including flatbed trailers, enclosed trailers, refrigerated trailers, and tank trailers. The type of trailer used depends on the specific needs of the cargo being transported.

## What is the maximum weight that a truck can pull?

The maximum weight that a truck can pull varies depending on the type and size of the truck, as well as the type of trailer being pulled. Generally, a semi-truck can pull up to 80,000 pounds, while a heavy-duty pickup truck can pull up to 18,000 pounds.

## What safety precautions should be taken when truck pulling trailer?

When truck pulling trailer, it is important to ensure that the trailer is properly attached to the truck, the cargo is loaded and secured correctly, and the truck is in good working condition. It is also important to follow traffic laws and maintain a safe speed while driving.

## What are the benefits of truck pulling trailer?

Truck pulling trailer offers many benefits, including the ability to transport large and heavy items, increased efficiency and cost-effectiveness compared to other modes of transportation, and the flexibility to transport a variety of cargo types. It is also a common method of transportation for businesses and individuals alike.

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