# Mechanical Engineering - Strength of Materials - Discussion

Discussion Forum : Strength of Materials - Section 1 (Q.No. 8)
8.
Two shafts 'A' and 'B' transmit the same power. The speed of shaft 'A' is 250 r.p.m. and that of shaft 'B' is 300 r.p.m. The shaft 'B' has the greater diameter.
True
False
Explanation:
No answer description is available. Let's discuss.
Discussion:
52 comments Page 1 of 6.

Ram said:   4 years ago
Interms of speed, we use less diameter shafts.
(2)

Bumba said:   5 years ago
Speed is inversely proportional to the Dia of shaft.
(10)

Rajneesh singraul said:   5 years ago
Shaft rpm can not determine by diameter. It Can be determined by hollow shaft and solid shaft.
(5)

Bhargav Panchal said:   5 years ago
v = π * D * N/60.

From this v is proportional to diameter and N both. So, I think the statement is true.
(1)

Muswar_SIYAL said:   6 years ago
Here the term "Two shafts ' is used.

Not Two Pulleys, so that I think no relation.
(2)

Harshal Dongre said:   6 years ago
P=(2*π*N*T/60).
So for same power, NT=Constant.
Therefore for less rpm more torque is transferred, so greater the torque greater is the diameter.
(6)

BRIJ MOHAN VERMA said:   6 years ago
Diameter of a shaft in any power transmission is directly proportional to shaft speed.
(1)

Kartik Uttarkar said:   6 years ago
If the RPM is increasing then diameter value should be small but not big. And vice-versa if the RPM value is decreasing then it should have bigger diameter.
(1)

Govind kumar said:   6 years ago
If dia of shaft is small then it's rotation is more than the larger dia of shaft.

Kishan P said:   6 years ago
As Rpm increasing, torque in reduces. As torque reduce the maximum shear stress at the outer most fibre will reduce.

As it's having less shear stress, it required smaller diameter.

Hence when Rpm increasing, the diameter will be smaller When compared to a member having lower Rpm.