What Is the Initial Velocity of a Ball Thrown Upwards from a Building?

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To determine the initial velocity of a ball thrown upwards from a 20.0m high building, the formula x = xo + vot + 1/2at^2 can be used. The total time for the ball's flight is 5.5 seconds, which is crucial for calculations. It's important to establish positive and negative directions before applying the formula to avoid confusion in the results. Properly defining these directions ensures accurate calculations of the initial velocity. Understanding these principles is essential for solving similar physics problems effectively.
petal5
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The question is as follows:

A man stands at the edge of the roof of a building 20.0m above the ground.He throws a ball vertically straight upwards(it just misses the edge of the building as it falls back down).If the total time taken for the ball to travel from his hand to the ground is 5.5seconds what is the initial velocity of the ball?

My question is,is it correct to use the following formula to solve the problem: x=xo + vot + 1/2at^2

Thanks!
 
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Yes, it is. However, do be careful when dealing with the directions. Define ur +ve and -ve directions first.
 
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The book claims the answer is that all the magnitudes are the same because "the gravitational force on the penguin is the same". I'm having trouble understanding this. I thought the buoyant force was equal to the weight of the fluid displaced. Weight depends on mass which depends on density. Therefore, due to the differing densities the buoyant force will be different in each case? Is this incorrect?

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