Unknown mass on a pulley system - Help

In summary, the 100 kg block takes 6.0s to reach the floor 1.0m below after being released from rest. The mass of the block on the left is 100 kg.
  • #1

Homework Statement


The 100 kg block shown in the diagram takes 6.0s to reach the floor 1.0m below after being released from rest. What is the mass of the block on the left?

Homework Equations


Newton's Third Law
F=ma
F (a on b) = -F (b on a)

The Attempt at a Solution



I don't even know where to start, I was sick last class and can't figure out how to do this from the textbook. I've tried so far:
T1 = tension rope 1
T2 = tension rope 2
t0= 0s
t1= 6s
d=1.0m
g=9.8m/s^2
m1=unknown, find
m2=100kg
mass M: Fy = 0
T1-mg=0
T1=mg

T2= mg = (100kg)(9.8m/s^2)
= 980N

And now I'm lost.
 

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  • #2
Start over.

(1) Calculate the acceleration from the given information.

(2) Apply Newton's 2nd law to each mass. This will allow you to solve for the tension in the rope and for the unknown mass.
 
  • #3
By using Newton's 2nd law,

d=0.5at2 (since v0 is zero),

I got an a=0.0556 m/s^2

Now, since they're on a pulley,

a= (m2g-m1g) / (m2+m1)

Plugging in, I get:

0.0556 = [(100kg*9.8m/s^2)-(m1*9.8m/s^2)] / 100kg + m1

rearranging, 5.56 + 0.0556 m1 = 980 - 9.8 m1
m1 = 100 kg

I know that's not the right answer, where am I going wrong?
 
  • #4
The only error I see is here:
dazedconfused said:
a= (m2g-m1g) / (m2+m1)
You have the signs of the two weights reversed. (Take positive to be in the direction of the acceleration.)
 

1. What is a pulley system?

A pulley system is a simple machine that consists of a wheel with a grooved rim and a rope or cable that runs along the groove. It is used to change the direction of a force and make it easier to lift heavy objects.

2. How does a pulley system work?

In a pulley system, the rope or cable is attached to the object being lifted and then looped around one or more wheels, called pulleys. By pulling on one end of the rope, the force is transmitted through the pulleys, allowing the object to be lifted with less effort.

3. What causes an unknown mass on a pulley system?

An unknown mass on a pulley system could be caused by various factors, such as an unbalanced load, an uneven distribution of weight on the pulleys, or a malfunctioning pulley. It is important to troubleshoot and identify the cause in order to properly address the issue.

4. How can I determine the mass on a pulley system?

To determine the mass on a pulley system, you can use the formula: mass = force / acceleration. By measuring the force applied to the rope and the acceleration of the object, you can calculate the mass. Alternatively, you can also use a scale to directly measure the mass of the object.

5. What should I do if I encounter an unknown mass on a pulley system?

If you encounter an unknown mass on a pulley system, it is important to first assess the situation and identify the cause of the issue. Then, you can make any necessary adjustments to the pulley system to balance the load and ensure safe and efficient operation. If the issue persists, it is best to consult a professional for further assistance.

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