Forces between two blocks on a frictionless surface

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Homework Help Overview

The problem involves two blocks, one on a frictionless surface and the other hanging, connected by a cord over a pulley. The objective is to calculate the acceleration of the first block, considering the effects of gravity and tension in the cord.

Discussion Character

  • Exploratory, Assumption checking, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the application of Newton's second law and the relationship between tension and gravitational force. There is an exploration of the variables used in the equations, particularly the definitions of the masses involved.

Discussion Status

The discussion has progressed with participants clarifying their understanding of the variables and equations. Some guidance has been provided regarding the correct application of mass in the calculations. There is an acknowledgment of a mistake in the initial approach, leading to a corrected calculation of acceleration.

Contextual Notes

Participants are reminded to include units in their answers and to consider significant figures based on the data provided. There is an ongoing inquiry about finding the tension in the system, indicating a continuation of the discussion beyond the initial problem.

Carmey
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Homework Statement



A block of mass 7.18 kg lies on a frictionless
horizontal surface. The block is connected
by a cord passing over a pulley to another
block of mass 5.6 kg which hangs in the air, as
shown. Assume the cord to be light (massless
and weightless) and unstretchable and the
pulley to have no friction and no rotational
inertia.

Calculate the acceleration of the first block.
The acceleration of gravity is 9.8 m/s^2
Answer in units of m/s

Homework Equations



Fnet=ma

The Attempt at a Solution


I used the equation Fnet=ma to find my horizontal equation T1-T2+M2G=MA
I then reduced that to M2G=MA since the two tensions are the same
After that I plugged in the numbers to get an acceleration of 9.8m/s^2
But i know this answer isn't right because when i checked it it was wrong
 
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Hi Carmey, welcome to PF!

You are right, the tension is the same along the string, so T1=T2.

What did you denote by M2 and what is M? Show your work in detail, please.

ehild
 
Sorry M2 is the mass of the second block (5.6 kg block) and M is the mass. I just figured out my mistake though, when i had the equation M2G=MA i forgot to use both masses for M. So when i did that I got the right answer of 4.294209703
 
Well done !:smile: But do not forget to add rthe unit (m/s2 ), and round off the result to so many significant digits as in the data.


ehild
 
Ya thanks i got that. I do have another question though if you could help me with that. How would you find the tension in the same problem?
 
Never mind i got it.
 

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