Question

A steel bar 35 mm x 35 mm in section and 100 mm in length is acted upon by a loud of 180 KN along its longitudinal axis and 400 KN and 300 KN along the axes of the lateral surface Determine

i) Change in the dimension of the bar

ii) Change in volume Take E = 205 Gpa and poissons ratio 0.3​

Answer 1

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The stresses in the direction of X, Y and Z

axes,

Vo)1 0.20 4G LTÉŽ KB/s 71

Along X-axes, Px=FxA=320*10360*60(N/ mm*mm)=88.89N/mm2

Along Y axis, Py=FyA=760*103180*60(N/ mm*mm)=70.37N/mm2

Along Z axis, Pz=FzA=600*103180*60(N/ mm*mm)=55.56N/mm2

Now, the strain along the three principal directions are, due to stresses, Px,Py,Pz,

ex=PxE-UPYE-uPzE

ex-88.89200*103-0.3*70.37200*103-

0.3*55.56200*103=0.000256

Now,

ey=PyE-uPzE-uPxE

ey=70.37200*103-0.3*55.56200*103- 0.3*88.89200*103=0.000135

ez=PzE-uPxE-uPyE

ez=55.56200*103-0.3*88.89200*103-0.3

*70.37200*103=0.00039

Volumetric sign=ex+eytez =0.000256+0.000135+0.00039

ev=0.000781

Also, volumetricstrain=changeinvolumeori ginalvolume

0.000781=changeinvolume18O*60*60

Also, volumetricstrain=changeinvolumeori ginalvolume

0.000781=changeinvolume180*60*60

Changeinvolume=506.088mm3

Now,ex=DeltaLL

0.000256-A180

AL=0.046mm

ey=DeltaWw

0.000135=AW60

AW=0.0081mm

ez=Deltatt

0.00039-At60

At=0.0234mm

Answer 2

Answer:

Fertilisation in a Flower

A pollen grain contains two male gametes. When a pollen grains falls on the stigma of the carpel, it grows a pollen tube downwards into the style. One of the male gamate reaches the ovary through pollen tube and fuses with egg to form zygote.

The other male gamate fuses with two polar nuclei one from each of embryo sac to form endosperm nucleus. This fission is called triple fission.