A 3 kg rock suspended above water weighs 29.4 N. When suspended beneath the surface of the water, its apparent weight is 28.2 N.
(a) What is the buoyant force on the rock?- i got 1.2 N which was correct
(b) If the container of water on a bathroom type scale weighs 9.8 N, what is the scale reading when the rock is suspended beneath the surface of the water?
THIS IS THE PART I CANT FIGURE OUT!!!
(c) What is the scale reading when the rock is released and rests at the bottom of the container?
This answer is 39.2 N
(a) What is the buoyant force on the rock?- i got 1.2 N which was correct
(b) If the container of water on a bathroom type scale weighs 9.8 N, what is the scale reading when the rock is suspended beneath the surface of the water?
THIS IS THE PART I CANT FIGURE OUT!!!
(c) What is the scale reading when the rock is released and rests at the bottom of the container?
This answer is 39.2 N
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The water is supporting an extra 1.2 N force due to the rock's presence.
The scale will read 9.8 + 1.2 = 11.0 N.
Another way to see it is looking at the net force on the system.
Rock and water pushing down minus the string pulling up.
9.8 + 29.4 - 28.2 = 11 N
The scale will read 9.8 + 1.2 = 11.0 N.
Another way to see it is looking at the net force on the system.
Rock and water pushing down minus the string pulling up.
9.8 + 29.4 - 28.2 = 11 N
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Well, before lowering, the rock weighted 29.4N. The weight of the rock will not change.
After lowering, the string is holding only 28.2N of the weight. The water (and therefore the container) must be supporting the (29.4 - 28.2) => 1.2N difference.
All of the rock's weight must be supported (or it would accelerate).
After lowering, the string is holding only 28.2N of the weight. The water (and therefore the container) must be supporting the (29.4 - 28.2) => 1.2N difference.
All of the rock's weight must be supported (or it would accelerate).