Mechanical Science 2

[mpc4000]

thanks for all your help on my last post the pennies are starting to drop and things are getting clearer but i still fall by the way side with calculations and onceagain i'm having trouble with this one

any help would be much appreciated thanks

[FONT=Geneva, Arial]A crane raises a 2.5 tonne load vertically in 4 minutes and 10 seconds. The crane motor is rated at 10kW. What is the vertical height to which to load is raised?[/FONT]

somehow got 101.9m once i;m sure that right but since then all my workings have gone ---- up

thanks aagin​

 

[j.mawer]

F=ma a=9.8m/s^2 m=2500kg so F=24500N
4min 10 secs = 250seconds

For motor Energy = 10000* 250 = 2 500 000J

Change in potential energy for load = Force * distance
assuming no loses
motor energy used = load potential energy gain
Power * time = Force * distance
2 500 000 = 24 500*distance
distance = 2 500 000 / 24500
=102m

 

[j.mawer]

Note I used gravity as 9.8 this time as corrected from last time, in my defense when I was at school not everyone could afford a calculator (many years ago) so all our exams had gravity = 10m/s^2 because it made the maths easy!

 

[telectrix]

when i went to school it was 32ft/sec sq. everything worked out right then. now i have to work out something in meters, then have to convert to something recognisable.

 

[j.mawer]

I thought I was getting old, but now I feel like a youngster again

 

[mpc4000]

thanks alot j mawer really need that checks in the post