Acceleration of a system with three blocks

AI Thread Summary
The discussion focuses on calculating the acceleration of a system with three blocks of different masses (9kg, 4kg, and 6kg). The user initially applied Newton's second law but overlooked the effect of gravity on the middle block (4kg). After realizing that gravity also impacts this block, the user adjusted their calculations, leading to the correct acceleration. The importance of including all forces acting on each block was emphasized. The user successfully resolved the issue after this clarification.
duplaimp
Messages
33
Reaction score
0

Homework Statement


888aSSy.jpg


What is the acceleration of this system?

Homework Equations


F=ma


The Attempt at a Solution


I tried the following:

Let blocks with mass 9kg, 4kg and 6kg be m9, m4, m6
This is the free body diagrams I drawn:

flDzVEo.png


Then I applied Newton's 2nd Law:
F = ma

(For m9) mg-TR=9a
(For m4) TR-TL=4a
(For m6) TL-w*sin(30)=6a

I solved for a and it didn't gave the right answer.
What I am doing wrong?
 
Physics news on Phys.org
duplaimp said:
(For m9) mg-TR=9a
Good.

(For m4) TR-TL=4a
What about gravity?

(For m6) TL-w*sin(30)=6a
Good.

Gravity applies to m4 just like it does to m6.
 
Doc Al said:
Gravity applies to m4 just like it does to m6.

I didn't included that because as m4 is "in the middle" I thought it wasn't necessary but it seems I was wrong. Now it gives the right acceleration.
Thank you! :biggrin:
 

Thread 'Errors and significant figures'

I multiplied the values first without the error limit. Got 19.38. rounded it off to 2 significant figures since the given data has 2 significant figures. So = 19. For error I used the above formula. It comes out about 1.48. Now my question is. Should I write the answer as 19±1.5 (rounding 1.48 to 2 significant figures) OR should I write it as 19±1. So in short, should the error have same number of significant figures as the mean value or should it have the same number of decimal places as...
View full post »
Thread 'A cylinder connected to a hanging mass'

Thread 'A cylinder connected to a hanging mass'

Let's declare that for the cylinder, mass = M = 10 kg Radius = R = 4 m For the wall and the floor, Friction coeff = ##\mu## = 0.5 For the hanging mass, mass = m = 11 kg First, we divide the force according to their respective plane (x and y thing, correct me if I'm wrong) and according to which, cylinder or the hanging mass, they're working on. Force on the hanging mass $$mg - T = ma$$ Force(Cylinder) on y $$N_f + f_w - Mg = 0$$ Force(Cylinder) on x $$T + f_f - N_w = Ma$$ There's also...
View full post »

Similar threads

Calculating acceleration of a prism and block connected to a wall through a rope and pulley
Replies
4
Views
325
Atwood's with a cylinder - Rotational Motion
Replies
13
Views
851
Find acceleration of Moving incline with a block on it
Replies
11
Views
3K
Block on top of an inclined plane, with a rough surface, that moves with constant acceleration
Replies
41
Views
3K
Dynamics of a Block on top of a slab with friction between them
Replies
33
Views
1K
Two Blocks and a Pulley Friction Problem
Replies
2
Views
4K
What will be the acceleration of a 10kg block w.r.t. the ground frame?
Replies
6
Views
2K
A block on an accelerating wedge
Replies
4
Views
2K
Find the mass of a block on an inclined pulley
Replies
3
Views
2K
What Force Keeps the Block from Sliding on a Frictionless Inclined Ramp?
Replies
10
Views
2K

Hot Threads

Recent Insights

Back
Top