Physics including a grindstone and torque? Can someone explain these answers ple
ID: 1488608 • Letter: P
Question
Physics including a grindstone and torque? Can someone explain these answers please?
Use the following situation for the next two problems: A grindstone 0.50 m in radius, of mass 45 kg, is rotating at 16 revolutions per second. The grindstone can be treated as a uniform cylinder. At t = 0 a tool is pressed against the rim of the grindstone causing it to slow down with a constant angular acceleration of 9.4 rad/s^2. How long does the grindstone take to come to rest? What is the net torque on the grindstone?Explanation / Answer
moment of inertia of solid cylinder is given by 0.5*mass*radius^2=0.5*45*0.5^2=5.625 kg.m^2
part a:
initial angular speed=16 rev/sec
=16*2*pi rad/sec
=100.531 rad/sec
final angular speed=0
angular acceleration=-9.4 rad/s^2
using the formula:
final angular speed=initial angular speed+angular acceleration*time
=>time=100.531/9.4=10.6948 seconds
hence option B is correct.
Q8:
torque=moment of inertia*angular accleration
=5.625*9.4=52.875 Nm
hence option D is the closest answer.