Angular Speed of Electric Fan: Calculations & Results

In summary, the initial angular speed of the electric fan running on HIGH is 175.409 rev/sec. The fan slows down to 98 rad/sec in 1.83 seconds after the LOW button is pushed. The blades of the fan have a radius of 0.62 meters and their deceleration rate is 42.3 rad/sec2. The formula used to calculate the initial speed was: final velocity = initial velocity + acceleration * time. The radius of the blades may be needed for future calculations.
  • #1
mattmannmf
172
0
An electric fan is running on HIGH. After fan has been running of 13.2 minutes, the LOW button is pushed. The fan slows down to 98 rad/sec in 1.83 seconds. The blades of the fan have a radius of 0.62 meters and their deceleration rate is 42.3 rad/sec2.

a) What was the initial angular speed of the fan in rev/sec?

i am pretty sure i have to use the equation:

angular velocity^2=angular velocity^2+2(angular accel)(angular disp)

we have
final velocity= 98
angular accel= -42.3
angular disp= unknown, but we have radius.
time= 1.83

would the angular disp be 2pi?
 
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  • #2
mattmannmf said:
would the angular disp be 2pi?
No. However, can you think of a better formula to use?
 
  • #3
perhapes angular veloctiy= initial angular velocity + ang accel*time?
 
  • #4
mattmannmf said:
perhapes angular veloctiy= initial angular velocity + ang accel*time?

That would be better.
 
  • #5
i tried that formula, but my answer wasn't correct...
 
  • #6
mattmannmf said:
i tried that formula, but my answer wasn't correct...
Perhaps if you detailed your working we could point out where you went wrong.
 
  • #7
final velocity= initial velocity+ acceleration*time

98= initial velocity+ (-42.3)(1.83)

175.409= initial velocity?
im pretty sure right off the bat that that is wrong because why would they give you the radius if you didn't need it... so the radius has to play a part into this.
 
  • #8
mattmannmf said:
final velocity= initial velocity+ acceleration*time

98= initial velocity+ (-42.3)(1.83)

175.409= initial velocity?
Looks good to me :approve:
mattmannmf said:
im pretty sure right off the bat that that is wrong because why would they give you the radius if you didn't need it... so the radius has to play a part into this.
Do you perhaps need the radius for one of the following questions?
 
  • #9
nope, its a 1 question problem...i tried that answer and it wasn't correct. so probably need the radius somewhere in there
 
  • #10
mattmannmf said:
nope, its a 1 question problem...i tried that answer and it wasn't correct. so probably need the radius somewhere in there
You're asked for the initial speed in revolutions per second rather than radians per second.
 
  • #11
ahhhh there's the problem..ok thanks!
 

What is angular speed?

Angular speed, also known as angular velocity, is a measure of how fast an object is rotating around a fixed point. It is typically measured in radians per second (rad/s) or revolutions per minute (rpm).

How is angular speed calculated for an electric fan?

The angular speed of an electric fan can be calculated by dividing the number of revolutions the fan makes in a given time period by the time taken for those revolutions. This calculation can be represented by the formula: angular speed = (number of revolutions) / (time taken).

What factors can affect the angular speed of an electric fan?

The angular speed of an electric fan can be affected by several factors, including the speed setting of the fan, the weight and size of the fan blades, the condition and cleanliness of the fan motor, and any external forces such as air resistance.

How does the angular speed of an electric fan impact its cooling effectiveness?

The angular speed of an electric fan is directly related to its cooling effectiveness. A higher angular speed means that the fan is rotating faster, which leads to a higher air flow and better cooling performance. However, the design and placement of the fan also play a significant role in its overall effectiveness.

What are some common methods for measuring the angular speed of an electric fan?

Some common methods for measuring the angular speed of an electric fan include using a tachometer, which measures the speed of rotation, or using a strobe light, which can be used to visually measure the rotation speed by adjusting the frequency of the strobe to match the fan's speed.

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