Seemingly simple mechanics questions

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In summary: This problem states that there is a box with weight mg and a string that is less of magnitude with tension t as shown in this picture. The question is what are two possibilities for this situation and the answers are : rising with a decreasing speed and falling with an increasing speed.
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werproc
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1. Homework Statement
The problem basically states that there is a box with weight mg and a string that is less of magnitude with tension t as shown in this picture: https://gyazo.com/efeb48469cfb44399bea6c2dcc9e87c7
The question is what are two possibilities for this situation and the answers are : rising with a decreasing speed and falling with an increasing speed. I do not understand the rising with a decreasing speed aspect of it in conceptual and mathematical terms. How does this happen (in what scenario for example)?

Homework Equations

:
F=ma, mg etc.[/B]

The Attempt at a Solution


It's obvious that acceleration is negative from the start as mg has the greater magnitude (T-mg/m = a)
my thought was we either have an initial tension that decreases of some sort or we have an initial velocity above 0 for the box and it decreases as time goes on
 
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  • #2
werproc said:
It's obvious that acceleration is negative from the start as mg has the greater magnitude (T-mg/m = a)
my thought was we either have an initial tension that decreases of some sort or we have an initial velocity above 0 for the box and it decreases as time goes on
Do not assume the system was previously at rest, with only mg and T<mg acting on it since. The object may have been given an initial speed by some some larger T, or by some other means.
 
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  • #3
That problems seems somewhat unspecific

I can think of scenarios in which at least the last two answers apply and possible the first two as well

I am curious as to what the answer is and why
 
  • #4
Kaura said:
That problems seems somewhat unspecific
I can think of scenarios in which at least the last two answers apply and possible the first two as well
I am curious as to what the answer is and why
Note the constraint mentioned here:
werproc said:
weight mg and a string that is less of magnitude with tension t
 

FAQ: Seemingly simple mechanics questions

What is the definition of mechanics?

Mechanics is a branch of physics that deals with the behavior and motion of objects under the influence of forces.

What are the three laws of mechanics?

The three laws of mechanics, also known as Newton's laws of motion, are: 1) An object at rest will remain at rest and an object in motion will remain in motion at a constant velocity unless acted upon by an unbalanced force. 2) The force applied to an object is equal to its mass multiplied by its acceleration. 3) For every action, there is an equal and opposite reaction.

What is the difference between statics and dynamics in mechanics?

Statics deals with the study of forces and objects at rest, while dynamics deals with the study of forces and objects in motion.

What is the unit of measurement for force in mechanics?

The unit of measurement for force in mechanics is the Newton (N). One Newton is equal to the force needed to accelerate a mass of one kilogram at a rate of one meter per second squared.

What is the difference between speed and velocity in mechanics?

Speed is a measure of how fast an object is moving, while velocity is a measure of how fast an object is moving in a specific direction.

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