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makeAwish
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Hello! May i ask a question?
Why angular acceleration is positive if object rotating clockwise is slowing down?
Thanks.
Why angular acceleration is positive if object rotating clockwise is slowing down?
Thanks.
Doc Al said:What's the direction of the change in angular speed?
Another example, for linear motion: Toss a ball straight up into the air. It's moving up and slowing down, but what's the direction of its acceleration?
Right.janettaywx said:the gravitational acceleration is always coming down.
so the ball's accel is downwards?
Right.janettaywx said:hmm. wait. say i define positive upwards, g is negative cos it is downwards.
The ball is moving upwards, but slowing down. So its acceleration is negative (downwards).the ball is deccelerating upwards so it is negative?
So which direction is its acceleration? Clockwise or counterclockwise? Then you can decide whether it should be called positive or negative.janettaywx said:but how abt an object rotating clockwise is slowing down?
The usual convention is that counterclockwise is positive and clockwise is negative.when it rotates clockwise, its angular speed is negative right?
i not sure the direction of angular speed as it is not stated in my notes.
This is true.my notes just say " angular acceleration is positive if object rotating counterclockwise is speeding up and angular acceleration is positive if object rotating clockwise is slowing down"
Ask yourself:janettaywx said:hmm. why " angular acceleration is positive if object rotating counterclockwise is speeding up and angular acceleration is positive if object rotating clockwise is slowing down" is true?
Doc Al said:Ask yourself:
A) If something rotating counterclockwise speeds up, which way is it accelerating? Clockwise or counterclockwise?
B) If something rotating clockwise slows down, which way is it accelerating? Clockwise or counterclockwise?
Then use the sign convention to determine whether it's positive or negative.
Sounds good, but with some comments. Careful with the term "decelerating"--I find it more confusing than helpful. (It just means "slowing down".) Much better to stick with acceleration, which can be positive or negative. So for B I would say it's moving clockwise but slowing down (decelerating), thus the acceleration is counterclockwise and thus positive.janettaywx said:A) it is accelerating counterclockwise as well so it is positive?
B) it is decelerating in clockwise direction (negative). which means it is accelerating in counterclockwise direction and so it is positive as well?
Angular acceleration is the rate of change of angular velocity, meaning how quickly an object's angular velocity changes over time. It is measured in radians per second squared (rad/s²) in the metric system.
Angular acceleration is caused by a net torque acting on an object, which is a force that causes rotational motion. This torque can be produced by a variety of factors such as gravity, friction, or applied forces.
Angular acceleration can be calculated by dividing the change in angular velocity by the change in time. The formula is: α = (ωf - ωi) / (tf - ti), where α is angular acceleration, ω is angular velocity, and t is time.
In clockwise rotation, the object rotates in the direction of decreasing angle values. This means that the angular velocity and angular acceleration will also have negative values, as they are defined as positive in the counterclockwise direction.
Angular acceleration affects an object's motion by changing its angular velocity, which in turn affects its rotational speed and direction. The greater the angular acceleration, the faster the object's angular velocity will change, leading to a more rapid change in its rotational motion.