Question

7. • A person walks into a room and switches on the ceiling fan. The fan accelerates with constant angular acceleration for 15 s until it reaches its operating angular speed of 1.9 rotations/s-after that its speed remains constant as long as the switch is “on.” The person stays in the room for a short time; then, 5.5 minutes after turning the fan on, she switches it off again and leaves the room. The fan now decelerates with constant angular acceleration, tak- ing 2.4 minutes to come to rest. What is the total number of revo- lutions made by the fan, from the time it was turned on until the time it stopped?

THE ANSWER IS 750 REV, I keep getting it wrong please show me the correct way to do it.

Answer 1

Average speed of the fan during acceleration and 1. deceleration = log = 0.95 not/sec Revolation made by the - fans during acceleration a average speed & time (acceleration) = 0098x15 = 14-25 rotations Revolution made by fan during a average speed x time deceleration . . (decelerations 50:99 x 24x60 = 136.8 rotations i

Seconds - Revolution made by fan during le by tan during - constant acceleration = lax (5.5x60 -15) 21.98 (330-15) = 598.5 Potal number of revolutions = 14:25+186-8+598.5 = ~ 449.55 750 revolutions.