Work to be performed by a pulley

[inverse]

Hello,
I have a doubt in this exercise because it does not relate the forces work to be done.

"The system shown is at rest. Determine the amount of work must be developed to apply a downward vertical force on the sphere, so that the block come off the floor."

http://s2.subirimagenes.com/imagen/previo/thump_7853867fisica1.png

Sphere;

[itex] F + P - T = ma [/itex]

Block;

[itex] F_E - P = ma [/itex]

How should raise it?

Thanks

 

[berkeman]

Hello,
I have a doubt in this exercise because it does not relate the forces work to be done.

"The system shown is at rest. Determine the amount of work must be developed to apply a downward vertical force on the sphere, so that the block come off the floor."

http://s2.subirimagenes.com/imagen/previo/thump_7853867fisica1.png

Sphere;

[itex] F + P - T = ma [/itex]

Block;

[itex] F_E - P = ma [/itex]

How should raise it?

Thanks

The link is not working for me...

 

[jedishrfu]

so it looks like you could reduce this problem by symmetry to simply lifting a 2kg weight off the ground with a spring attached to the string you're using.

Given that the weight is 2kg you can determine the downward force you must overcome and given the spring K you can use hooks law to determine the upward force as you raise the string. When they are balanced the weight should lift off the ground.

Does that sound right?

 

[Chestermiller]

If the system is initially at equilibrium, and the pulley's are frictionless, what is the tension on the string that connects the 2 kg weight to the top of the spring? What is the tension on the string connecting the bottom of the spring to the 4kg mass? How much does the tension in the string connecting the 2 kg mass to the top of the spring have to increase to just begin lifting the 4 lb mass? What will the tension on the string connecting the bottom of the spring to the 4 kg mass have to increase to? For that increase in the tensions, how much will the spring have to stretch? How much work does it take the stretch the spring this amount?

 

[Nickie]

for your question. In this scenario, the work to be performed by the pulley would involve transferring the force applied by the downward vertical force onto the sphere and block, allowing them to move in the desired direction (upwards). The pulley acts as a mechanical advantage by reducing the amount of force needed to lift the objects. The amount of work required would depend on the mass of the sphere and block, as well as the distance they need to be lifted. This work can be calculated using the formula W = Fd, where W is work, F is force, and d is distance.

In terms of the forces involved, the downward vertical force would provide the necessary force to lift the objects, while the tension in the rope connected to the pulley would help support the weight of the objects. The equation you provided shows the forces acting on the sphere and block, but it would also be important to consider the forces acting on the pulley itself, such as the tension in the rope and the weight of the pulley.

I hope this helps clarify the concept of work in relation to the pulley system shown in the exercise. It is important to understand the forces involved in order to accurately calculate the work required to lift the objects. If you have any further questions, please don't hesitate to ask.