Mechanical jack efficency

[Flimjabs]

hey team, I need help with the following question
a mechanical Jack is used to lift a load of 3kn, the mean diameter of the screw thread is 60mm and the pitch is 12mm, if the coefficient of friction is 0.26 calculate
a, the torque required to lift the load
b, the efficiency of the Jack
I have completed part A but i am struggling with part b, I have attached a photo of my working, any help to point me in the right direction would be appreciated
thanks

 

[Deleted member 4993]

hey team, I need help with the following question
a mechanical Jack is used to lift a load of 3kn, the mean diameter of the screw thread is 60mm and the pitch is 12mm, if the coefficient of friction is 0.26 calculate
a, the torque required to lift the load
b, the efficiency of the Jack
I have completed part A but i am struggling with part b, I have attached a photo of my working, any help to point me in the right direction would be appreciated
thanks

I see "?" in your response to part (b). You have an answer there - has that been already graded?

Your answer seems to be correct to me - except for converting to %

 

[Flimjabs]

I see "?" in your response to part (b). You have an answer there - has that been already graded?

Your answer seems to be correct to me - except for converting to %

The question was just look over by a tutor to try point me in the right direction, okay so just a conversion to 19.3%?, I somewhat questioned my calculations as 19.3% efficency seemed really low

 

[Deleted member 4993]

The question was just look over by a tutor to try point me in the right direction, okay so just a conversion to 19.3%?, I somewhat questioned my calculations as 19.3% efficency seemed really low

I did NOT check the numerical answer. However, your "process" is correct.