Power Transmitted by a Shaft in Torsion

Q. Two shafts A and B are made of the same material. The diameter of shaft B is twice that of shaft A. The ratio of power which can be transmitted by shaft A to that of shaft B is (If maximum shear stress remains the same)

1. $\frac{1}{2}$
2. $\frac{1}{4}$
3. $\frac{1}{8}$
4. $\frac{1}{16}$

Q. If the diameter of a shaft subjected to torque alone, is doubled, then the horse power P can be increased to

1. 16P
2. 8P
3. 4P
4. 2P

Q. What is the power transmitted by a 100 mm diameter soild shaft at 150 rpm without exceeding a maximum stress of $60N/m{m}^2$?

1. 187.5 kW
2. 18.75 kW
3. 1.875 kW
4. 1875 kW

Q. If a shaft is turning at N r.p.m and the mean torque to which the shaft is subjected is T N-m, the power transmitted by the shaft in kW would be

1. $\frac{2\pi NT}{45000}$
2. $\frac{2\pi NT}{60000}$
3. $\frac{2\pi NT}{30000}$
4. $\frac{2\pi NT}{33000}$

Q. A solid shaft of 80 mm diameter is transmitting 100 kW of power at 200 r.p.m. The maximum shear stress induced in the shaft will nearly be

1. $60N/m{m}^2$
2. $56N/m{m}^2$
3. $52N/m{m}^2$
4. $48N/m{m}^2$

Q. A shaft turns at 150 rpm under a torque of 1500 Nm. Power transmitted is

1. $15\pi kW$
2. $10\pi kW$
3. $7.5\pi kW$
4. $5\pi kW$

Q. A solid shaft rotating at 180 rpm subjected to a mean torque of 5000 N-m. What is the power transmitted by the shaft in kW?

1. $25\pi$
2. $20\pi$
3. $60\pi$
4. $30\pi$

Q. Assertion (A) : A hollow circular shaft has more power transmitting capacity than a solid shaft of same material and same weight per unit length.

Reason(R): In a circular shaft, shear stress developed at a point due to torsion is propotional to its radial distance from the centre of the shaft.

1. both A and R are true and R is the correct explanation A
2. both A and R are true but R is not a correct explanation of A
3. A is true but R is false
4. A is false but R is true

Q. A hollow steel shaft has outside diameter d and inside diameter d/2. The value of d for the shaft, if it has to transmit 200 hp at 105 rpm with a working shear stress of $420kg/c{m}^2$, is

1. 5.6 cm
2. 2.6 cm
3. 12.1 cm
4. 15.5 cm

Q. A circular shaft rotates at 200 rpm and is subject to a torque of 1500 Nm. The power transmitted would be

1. $10\pi kW$
2. $15\pi kW$
3. $20\pi kW$
4. $30\pi kW$

Q. A metal shaft of solid circular section rotates at 160 rpm and is subjected to a torque of 1500 Nm. What is the power, in kW, transmitted by the shaft?

1. $32\pi$
2. $16\pi$
3. $12\pi$
4. $8\pi$

Q. A solid shaft transmits 150 kW at a shear stress of 70 MPa running at a frequency of 3 Hz. What will be the shear stress when the frequency is 1.5 Hz?

1. 35 MPa
2. 50 MPa
3. 57 MPa
4. 140 MPa

Q. Two steel shafts A and B are used for transmitting power. The ratio of revolutions of shafts i.e., $\frac{N_A}{N_B}=2.$ The ratio of torques on shafts i.e., $\frac{T_A}{T_B}=\frac{1}{2}$. The ratio of the horse power transmitted by the shafts i.e. $\frac{P_A}{P_B}$ would be

1. 1/2
2. 1/4
3. 1
4. 2

Q. A hollow shaft $d_0=2d_i$ (where $d_0$ and $d_i$ are the outer and inner diameters respectively) needs to transmit 20 kW power at 3000 RPM. If the maximum permissible shear stress is 30 MPa, $d_0$ is

1. 11.29 mm
2. 22.58 mm
3. 33.87 mm
4. 45.16 mm

Q.

A car of mass 1000 kg travels at 12 m/s on a horizontal and the resistance to motion is 500 N. Find (c) the power developed by the engine.

Q. The power transmitted by a 75 mm diameter shaft at 140 r.p.m., subjected to a maximum shear stress of $60N/m{m}^2$, is nearly

1. 68 kW
2. 70 kW
3. 73 kW
4. 76 kW

Q.

A pulley system has $\mathrm{MA}=4$. If a load of $10\mathrm{kgf}$ is pulley by a distance of $2\mathrm{m}$ in $10\mathrm{s}$, calculate the power developed by the effort.

1. $15\mathrm{w}$

2. $20\mathrm{w}$

3. $25\mathrm{w}$

4. $4.9\mathrm{w}$

Q. If a shaft rotates at 100 r.p.m and is subjected to a torque of 3000 N-m, the power transmitted in kW would be

1. $30\pi$
2. $15\pi$
3. $20\pi$
4. $10\pi$

Q. A motor driving a solid circular steel shaft transmits 40 kW of power at 500 rpm. If the diameter of the shaft is 40 mm, the maximum shear stress in the shaft is ______ MPa.

1. 60.792