How to get acceleration of 1.44 m/s² in a tension problem

[Garrett21]

Can someone please tell me how my teacher got Acceleration of 1.44m/s^2?
I don't see how its even possible without another force acting on the object

 

[Chestermiller]

Can someone please tell me how my teacher got Acceleration of 1.44m/s^2?
I don't see how its even possible without another force acting on the object

Is it possible that the pulley has specified mass and radius in the problem statement?

Chet

 

[Garrett21]

Is it possible that the pulley has specified mass and radius in the problem statement?

Chet

No, she is just introducing this so there is no friction.. I was scratching my head while everyone was saying they got the same answer following instructions, but i vaguely disagreed with it so that's why I am asking here.

 

[oddjobmj]

This seems to be a poorly designed problem. If you use F=ma and assume the pulley to be frictionless and massless you get a=(9.8)(5)/(15)=3.27 m/s^2

It seems that there is some assumed mass in the pulley though because they give you the distance it falls and the time it takes. Using those in the following kinematic equation yields an acceleration of 1.39 m/s^2 which is close:

x=x₀+v₀t+$\frac{1}{2}$at²

 

[Chestermiller]

No, she is just introducing this so there is no friction.. I was scratching my head while everyone was saying they got the same answer following instructions, but i vaguely disagreed with it so that's why I am asking here.

What were the instructions? I got the same results as oddjobmj.

Chet

 

[Garrett21]

What were the instructions? I got the same results as oddjobmj.

Chet

Just to find the acceleration at 1m... idk why this problem is annoying me so much but realistically on a test, i should write.. "this problem is not frictionless"

 

[Chestermiller]

One more thing. Are you sure the mass of A wasn't 30 Kg?

Chet

 

[Garrett21]

One more thing. Are you sure the mass of A wasn't 30 Kg?

Chet

Yes 100% if the mass was 30kg would the acceleration be equal to what the problem states?

 

[Chestermiller]

Yes 100% if the mass was 30kg would the acceleration be equal to what the problem states?

Yes, pretty close.

chet