Pulley problem using 2nd Law of motion

In summary, the conversation discusses a system with a 1 kg hanging off the table and a string connected to a 10 kg weight, with a 5 kg weight on the other side of the 10 kg weight. The system is moving to the left at 2 m/s and the question is whether there is an acceleration to the right due to the larger weight. The conversation also touches on finding the kinetic coefficient of friction, tensions in the strings, and the possibility of deceleration or acceleration depending on the net force. The system is assumed to slide without collision with the pulleys. The final problem is to find when the system stops moving to the left and how far left it will go, with a calculated acceleration of 2
  • #1
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This is hard to explain without having a picture, but there is a 1 kg hanging off the table. And a string is connected from that to a 10kg weight. From that weight on the other side, a 5kg weight hangs off the table. They system is moving to the left at 2 m/s. Do I have to compensate for that in any of my calculations because I believe it accelerates to the right b/c of the larger weight.
 
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  • #2
OK, is the speed constant at 2 m/s? If so then the net force is zero, because there is no acceleration.

Presumably the 5 kg weight is falling, the 1 kg weight is rising, and the 10 kg weight is resisting the motion with friction.

Are you trying to find the dynamic or kinetic coefficient of friction for the 10 kg mass, or tensions in the strings?
 
  • #3
Sorry, I forgot to include those parts in the problems.
Disregard all friction. It doesn't indicate a constant velocity so I am assuming there is an acceleration.

To find the acceleration I used a system consisting of T1-W1=m1a; T2-W2=-m2a; and T2-T1=m3a. This is a probably a dumb question, but the system can still acclerate to the right even though it is moving the left, right?

What I have left to find in this problem is when the system stops moving to the left and how far left. I'm pretty sure I can figure that out using simple kinematics.
 
  • #4
I have to pop out for little while, but I shall return.

Meanwhile, please elaborate on the which weight is on which side.

If the 2 m/s is an instantaneous velocity, then yes there could be an acceleration involved. Not knowing the initial conditions though, the system could be decelerating or accelerating, depending on the net force.

I presume then 10 kg mass slides across the table?
 
  • #5
1 kg is on the left, 10kg is on the table, and 5 kg is on the right. It's really a simple problem, you don't have to consider much else (like friction or anything). I'm using the 2m/s as an inital velocity. The problem states "Assume the table to be sufficiently long for the motion to occur without collision with the pulleys."
I got the acceleration to be 2.45m/s2 to the right but I didn't know if that could be, if the movement was to the left.
 
  • #6
yes, that's right.
 

FAQ: Pulley problem using 2nd Law of motion

What is the 2nd Law of Motion and how does it relate to pulley problems?

The 2nd Law of Motion, also known as Newton's Second Law, states that the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass. In the case of pulley problems, the 2nd Law of Motion applies because the forces acting on the pulley and the objects connected to it (such as the rope or weights) determine the acceleration and motion of the system.

How do you determine the net force in a pulley problem using the 2nd Law of Motion?

In order to determine the net force in a pulley problem, you must first identify all the individual forces acting on the objects connected to the pulley. These forces include the weight of the objects (mg), the tension in the rope (T), and any other external forces. Then, using the 2nd Law of Motion formula (F=ma), you can calculate the net force by summing up all the individual forces in the system.

What is the role of friction in a pulley problem using the 2nd Law of Motion?

Friction is an important factor to consider in pulley problems using the 2nd Law of Motion. In most cases, friction acts in the opposite direction of motion and can therefore decrease the net force and acceleration in the system. This is especially important when determining the tension in the rope, as friction can cause the tension to be lower than expected.

Can the 2nd Law of Motion be applied to a pulley system with multiple ropes and pulleys?

Yes, the 2nd Law of Motion can be applied to more complex pulley systems with multiple ropes and pulleys. In these cases, it is important to break down the system into smaller parts and analyze each part separately, taking into account the forces and accelerations in each section. Then, the net forces and accelerations can be determined for the entire system by combining the results from each individual part.

What are some common mistakes when applying the 2nd Law of Motion to pulley problems?

One common mistake is forgetting to include the weight of the pulley itself in the calculations. The weight of the pulley can affect the net force and acceleration of the system. Another mistake is not considering the direction of friction, as it can impact the tension in the rope and the overall motion of the system. It is also important to double check the direction of the forces, as a mistake in direction can lead to incorrect calculations and solutions.

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