Civil Engineering - Strength of Materials - Discussion

The right answer is 0.0275mm.

P = 3000kg = 30000N,
L = 5000mm,
D = 20mm,
E = 2.1*10^6 N/mm^2.
So elongation = 30000*5000*4/3.14*400*2.1*10^6,
Ans = .2274... = 0.2275.

C is the correct answer.

0.02275 is the right answer.

A = 314.16,
P=3000kg=3000*10=30000N,
L=5m=5000mm,
E=2.1*10^6.

Elongation= Pl/AE.
= (30000* 5000)/(314.16 * 2.1 * 10^6).
= 0.2275 mm.
So, B is the right answer.

Given;

dl = (PxL)/(A.xE)
P = 3000kg, L=5m = 500cm.
A = 3.14x (2/2)>^2 = 3.14 cm^2.
E = 2.1x10^6 it/cm^2.

Putting the values in the formula.
dl = (3000kg x 500cm)/(3.14cm^2x2.1x10^6kg/cm^2).

Deduct the dimensions and zero we get;
dl= (15/3.14x2.1x10)=15/65.94=0.2275mm.
So, Answer :B

Units of E is in kg/cm2. So the answer is A.

@All.

A) If we convert all the necessary data into "mm" & keeping load in "kgs",
We get,
(3000*5000)/(314.16*2.1e^6) = 0.0227 mm.

B) If we covert the data in "cm", we get
(3000*500)/(3.142*2.1e^6) = 0.2273 cm.

C) If we convert only length in "mm" & keeping dia in "cm" we get,
(3000*5000)/3.142*2.1e^6) = 2.274 unknown units and wrong procedure.

D) If we convert load in "N" & all dimensions in "cm", we get
(3000*9.81*500)/(3.142*2.1e^6) = 2.230 cm.

E) If "E" is given in Kgs/cm^2, we get
(3000*5000)/(314.16*2.1e^8) = 0.0002274 mm, which is not in the given answer.

But the given answer is in "mm", and the correct one is "C" which is in "mm"

2. 274 is the correct answer.

dia=2cm, A=3.1416cm^2,
P=3000kg, L=5m=500cm, (E=2.1*10^6 Kg/cm^2)

Now, (PL/AE)={(3000*500)/(3.1416*2.1*10^6)} {(kg*cm)/(cm^2*(kg/cm^2))}

PL/AE= {(15*10^5)/(3.1416*21*10^5)} (cm)
PL/AE=0.22736cm =2.274~ 2.275mm.
So, answer is 2.275mm.