Question

The resisting torque on the crank of a riveting machine is as shown in the figure below. The duration of the cycle is 2 seconds. The motor driving the machine, however, has a speed of 1500 rpm and it delivers constant torque. The crankshaft of the machine is geared to the motor shaft. Neglecting frictional losses, The constant torque supplied by motor is ____ (N-m)

• A. 9.25

Answer 1

The correct option is A 9.25
Energy required by the machine per cycle

$=200\times 2\pi +\frac{1}{2}\times (\frac{\pi }{2}+\frac{\pi }{4})\times 1400$

$=(40+525)\pi =925\pi$

$\text{Power of the motor}=\frac{\text{Energy}}{\text{Time period}}=T_s\times \omega$

$=\frac{925\pi }{2}=1.45kW$

$T_s\times \omega =1452.25$

$T_s=\frac{1452.25}{2\pi \times 1500}\times 60=9.25N-m$