Solving Force Problem: Finding Velocity and Force Requirements

[the_d]

My problem is to find the force needed to give the system of bodies a velocity of 30 ft/s after moving 20 ft. from rest.

Can anyone help me with this? All i have done is found EFx and EFy for the 50lb weight

 

[radou]

Didn't you post this question earlier? (Or was it someone else with the same question?) As said, use the fact that the work done by that force on the distance of 20 ft equals the change of kinetic energy.

 

[the_d]

is there an equation for that??

 

[radou]

is there an equation for that??

If you know the definition of work, and the definition of kinetic energy, you should be able to write down this equation yourself.

 

[the_d]

so W = KE, where does the coeffeficient of kinetic friction play in all this??

 

[radou]

so W = KE, where does the coeffeficient of kinetic friction play in all this??

You didn't mention any kinetic friction coefficient.

 

[the_d]

sorry, the kinetic friction is 0.20...

 

[the_d]

does that play a role??

 

[radou]

does that play a role??

Yes, it does, because you have to include the force of friction into your sum of forces acting on the object.

 

[the_d]

ok, i got ya