# What maximal load can be lifted from a depth of 1000 m ?

1. Aug 16, 2006

### teng125

A steel rope consists of 100 rods. The diameter of each rod is 2 mm. The allowable rope stress is 130 N/mm^2.

what maximal load can be lifted from a depth of 1000 m ?

i use 100*130 N/mm^2 = 4*F(max) / pi * (4)

in order to find F(max).Am i correct??how can i use the length given??

thanx

2. Aug 16, 2006

### Astronuc

Staff Emeritus
One cannot multiply the stress by the number of rod. The stress in each rod is a maximum of 130 N/mm2.

Each rod can carry a load, so F = Stress * area, then F(rope) = 100 * F(rod). However, the steel rope must lift its weight (mass), so one has to subtract the weight of 1000 m of rope. Density of steel is about 800 kg/m2, and g = 9.81 m/sec2.

Now there is a question about depth - depth in what medium - air or water? The steel would have some bouyancy in water, but not air.

3. Aug 17, 2006

### teng125

think itis in just air.so how can we use the depth in the calculation??

4. Aug 17, 2006

### teng125

"F(rope) = 100 * F(rod). " the 100 is not the number of rods

5. Aug 17, 2006

### teng125

number of rods is not given and have to find