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The drawing shows a golf ball passing through a windmill at a miniature golf course. The windmill has 12 blades and rotates at an angular speed of 1.35 rad/s. The opening between successive blades is equal to the width of a blade. A golf ball (diameter 4.50 10-2 m) has just reached the edge of one of the rotating blades (see the drawing). Ignoring the thickness of the blades, find the minimum linear speed with which the ball moves along the ground, such that the ball will not be hit by the next blade

2 Answers

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Final answer:

To calculate the golf ball's minimum linear speed to avoid being hit by the next windmill blade, we derive the time it takes for one blade to pass and then determine the speed that allows the ball to travel its own diameter within that time.

Step-by-step explanation:

Calculating the Minimum Linear Speed for a Golf Ball

To calculate the minimum linear speed at which the golf ball must move to not be hit by the next blade of the windmill, we have to consider how long it takes for one blade to move out of the way and the next one to enter the same position. Since the windmill has 12 blades and rotates with an angular speed of 1.35 rad/s, the time for one blade to pass and create space for the golf ball is the time it takes for the windmill to rotate the angle equivalent to one blade width plus one opening.

First, we find the time for one complete revolution by taking the ratio of 2π radians to the angular speed:
T = 2π / ω, where ω is the angular speed.

Then we divide T by the number of blades to find the time for one blade to pass:
t = T / 12.

Because the ball's diameter is 4.50 x 10-2 m and it has to pass through an opening of the same size, it needs to clear the space within the time t. Therefore, its minimum speed is the diameter divided by t: v = d / t.

Using these steps, we can find the required linear speed for the golf ball to avoid the next blade.

User Manoj Kadolkar
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Answer:

vmin = 0.23 m/s

Step-by-step explanation:

The golf ball must travel a distance equal to its diameter in the time between blade arrivals to avoid being hit. If there are 12 blades and 12 blade openings and they have the same width, then each blade or opening is 1/24 of a circle of is 2π/24 = 0.26 radians across.

Therefore, the time between the edge of one blade moving out of the way and the next blade moving in the way is

time = angular distance/angular velocity

⇒ t = 0.26 rad / 1.35 rad/s = 0.194 s

The golf ball must get completely through the blade path in this time, so must move a distance equal to its diameter in 0.194 s, therefore the speed of the golf ball is

v =d/t

⇒ v = 0.045 m / 0.194 s = 0.23 m/s

User JShorthouse
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