# Mechanical Engineering - Strength of Materials - Discussion

Discussion Forum : Strength of Materials - Section 1 (Q.No. 10)
10.
The stress induced in a body, when suddenly loaded, is __________ the stress induced when the same load is applied gradually.
equal to
one-half
twice
four times
Explanation:
No answer description is available. Let's discuss.
Discussion:
25 comments Page 1 of 3.

Akshay patil said:   1 decade ago

Dara Singh said:   1 decade ago
Twice stress why & which formula used this it may be more than twice or little less than twice.

When the load is applied slowly due to viscous dissipation by the atmosphere only half of the energy is stored as compared to the case when the load is applied suddenly.

Siva bala said:   1 decade ago
In case of impact loading the dynamic force experienced by the body is given by P(dyn.) = W*[1+sqrt(1+2h/D)].

Here P = dynamic load experienced by the body.
W = static load which is impacting.
D = stact deflection due to above load.
h = height from which load is acting.

In this case h=0, So dynamic load experienced by the body is twice the load applied. As load to area is stress so stresses induced will be twice.

It is experimentally proved that the stress developed by impact load is twice than developed by gradually applied load.

AMAN said:   10 years ago
When we loaded suddenly load 'w' then we consider 'w' load in stress while we loaded gradually load "w' then we consider average value of 'w' which will be w/2 in the stress calculation.

So we know that,

So p1 = w/area.

And p2 = (w/2)/area.

So p1/p2 = [w/aria]/[ (w/2) /aria].

So p1/p2 = 2.

p1 = 2p2.

Sanjay said:   10 years ago
Because new load is P=P1+P2, where P1=P2 so the stress is twice.

Rishi said:   9 years ago
@Aman.

How can you say that the average load is w/2?

In case w is split into 4 loads (w1+w2+w3+w4) applied gradually then average would come w/4.

In this case answer would come 4 times. Your method is completely wrong.

Krishna said:   9 years ago
Stress do not depend on rate of application of force I prefer equal in both the cases.