Question

A disk has rotational inertia 1.22 x 10${}^{-3}$ kg-m${}^2$ and is attached to an electric drill whose motor delivers a torque of 15.8 N-m.

The angular momentum of the disk 33 ms after the motor is turned on is:

• A. 0.256 $kg-m^2/s$
• B. 1.012 $kg-m^2/s$
• C. 0.158 $kg-m^2/s$
• D. 0.521 $kg-m^2/s$

Answer 1

The correct option is D 0.521 $kg-m^2/s$

$\overline{c}=I\alpha$
$15.8=1.22\times {10}^{-3}\times \alpha$
$\alpha =1.3\times {10}^4$
$\omega =\alpha t$
$=1.3\times {10}^4\times 33\times {10}^{-3}$
$=427.37$
$L=I\omega$
$=1.22\times {10}^{-3}\times 427.37$
$=0.5214$