Answer :
The Physics problem involves finding the number of revolutions a pulley makes before stopping when subjected to friction. By computing the average angular velocity over the stopping time and converting time to minutes, the pulley is found to make 400 revolutions. So the correct option is c.
The subject of the question is Physics, specifically relating to rotational motion and rotational dynamics.
To solve the problem, we need to find out how many revolutions the pulley makes before coming to rest when it is brought to a stop by a constant force of friction. The pulley is initially rotating at 600 revolutions per minute (rpm).
Since the pulley takes 80 seconds to come to a halt, we can calculate the average angular velocity over the 80 seconds. This is halfway between the initial and final angular velocity, which is 600 rpm (initial) and 0 rpm (final). Hence, the average angular velocity is 300 rpm.
Now, we can calculate the total number of revolutions the pulley makes in 80 seconds by using the formula: Total Revolutions = Average Angular Velocity (in rpm) times Time (in minutes).
Converting 80 seconds into minutes gives us approximately 1.333 minutes.
So, the total revolutions are: Total Revolutions = 300 rpm times 1.333 min = 400 revolutions.
Hence, the correct option from the list is C. 400.
