# What's the least force we should apply?

• PhysicS FAN
In summary, the problem involves two objects of equal mass connected by a thread with a resistibility limit of 20N. The question is asking for the minimum force that needs to be applied to break the thread. To solve the problem, one must consider all the forces acting on the system and use Newton's laws of motion. By setting up equations for the forces and using the fact that the tension is equal to the mass times acceleration, the minimum force needed is calculated to be 40N.
PhysicS FAN

## Homework Statement

2 objects of the same mass are on a non-frictional level and are connected with a thread which has a resistibility limit T=20N. What is the least froce we should apply so that the thread breaks?

## The Attempt at a Solution

I don't know how to proceed with this problem since the system contains of 2 objects. My first thought was to use kinetic energy theorem on the first body since Kτελ-Καρχ=0 and then find a relationship with the tension of the thread and the force based on the energy theorems but that didnt work. Please help me

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You need to think about all the forces on your system.

PhysicS FAN
PeroK said:
You need to think about all the forces on your system.
Yes there's the force that we apply and the tension.

PhysicS FAN said:
Yes there's the force that we apply and the tension.

What happens when you apply a force?

PhysicS FAN
PeroK said:
What happens when you apply a force?
Well in this case the force will accelerate the system which may or may not had an initial velocity. If the force is big enough it will break the thread. Now after the thread breaks the left object will continue moving with the speed it had just before the moment that the break of the yarn happened because there is no friction and accroding to Newtons 1st Law it will continue moving. In the left object the force that is causing the acceleration is the tension of the thread so T=m*a . In the second object the tension is in the opossite direction of the force so: F-T=m*a. Now if we solve for F we get F=m*a+T . But from the first equation we know that m*a= T and so the force is equal to F=2T=2*20=40N.
I don't know what you did but you helped me solve the problem with only a question. Thank you!

Delta2 and PeroK

## What is force and why is it important?

Force is a physical quantity that can change the state of motion or shape of an object. It is important because it is necessary for movement, work, and many other phenomena in the physical world.

## What is the unit of force?

The unit of force is the newton (N) in the International System of Units (SI). Other common units include pounds (lb) and kilograms-force (kgf).

## What factors determine the least force that should be applied?

The least force that should be applied depends on the mass of the object, the desired acceleration, and the frictional forces acting on the object.

## How do we calculate the least force that should be applied?

The formula for calculating force is F=ma, where F represents force, m represents mass, and a represents acceleration. To calculate the least force, you would need to know the mass of the object and the desired acceleration.

## Why is it important to apply the least force possible?

Applying the least force possible is important because it minimizes the risk of causing damage or injury. It also helps conserve energy and resources.

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