VDU_Physics_1_011  
VirtualDynamics.OrgSolved UniversityPhysics ProblemsPhysics 1. Mechanics: Accelerated Circular MotionJavier Montenegro Joo Return to index page of Mechanics Problems Return to VirtualDynamics University home page




Accelerated Circular Motion.  
[1]
A disk of 2.5 kg and
1 m diameter is rotating at 3000 rpm when it is disconnected from the
source of energy that keeps it rotating. For the moment just before disconnection
calculate: (a) angular speed of the disc (b) tangential speed of a point
on the edge of the disc, (c) centripetal acceleration of a point on the
edge of the disc (d) If the disk stops 30 s after disconnection,
determine how many turns are completed during that time.
Solution.


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[2]
A 2.50 m diameter disk starts rotating with an angular speed of 1.75 rad/s
and a constant acceleration of 1.60 rad/s^{2 }. For a dot at
the edge of the disk and for 1.50s after initiated the motion,
calculate: (a) Displacement, (b) Angular velocity, (c) Tangential
velocity, (d) Magnitude of the acceleration vector, (e) Angle between
acceleration and radius. Solution.


[3]
When the motor of a
34 cm diameter disk which is rotating at 180 rpm, is turned off, the
disk gradually comes to rest in 18 s. Determine: (a) angular
acceleration of the disk. (b) Its average angular speed (c) Number of
turns completed until the disk stops (d) Displacement of a point on the
edge of the disk until this comes to stop.
Solution.


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[4] A 90cm diameter wheel is rotating at 250 Rpm when the brakes are applied for 30 seconds and at the end of that time the wheel has reduced its velocity in 40%. Determine: (a) Acceleration experimented by the wheel (b) Number of turns completed during the time the brakes are applied (c) Distance covered by an edge point of the wheel during the time the brakes are applied. Solution.


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[5] A disk of 25 kg and 1.80 m in diameter is spinning at 5000 Rpm, when the engine that keeps it rotating is switched off. Before turn off engine, calculate: (a) speed of the disk. (b) Speed of a point on the edge of the disk. (c) The centripetal acceleration of a point on the edge of the disk. (d) If the disk stops 3 min after turning off the engine, calculate how many turns are completed in that time. Solution.


[6] A 1.25m diameter disk that is at rest receives a constant acceleration of 0.40 rad/s^{2} during 5 minutes, and then the acceleration is turned off. Determine: (a) Number of turns completed during the 5 minutes (b) Maximum speed reached during the 5 min. (c) Time to stop after disconnecting the acceleration. (d) Number of turns completed after disconnecting the acceleration. Solution.


[7] A 120 gr ball is
tied to the end of a string of 3 m which is rotating with its other end
fixed to a rotating shaft. The ball describes a circular orbit and moves
with an acceleration of 10 m/s^{2 }. When the acceleration
vector makes an angle of 25^{o} with rope, calculate (a) radial
acceleration (b) tangential acceleration (c) speed of the ball.
Solution.

