# Questin about moving an object through liquid

• kevinf
In summary, the problem asks to calculate the force required to pull a copper ball of radius 2.50 cm upward through a fluid at a constant speed of 9.00 cm/s. The drag force is assumed to be proportional to the speed with a proportionality constant of 0.950 kg/s and the buoyant force is ignored. To solve this, one can draw a free body diagram and set the upward force equal to the sum of the downward forces (gravity and drag) since the net force must be zero for constant speed. The equation given in the problem may not be correct, but it can be modified to find the drag force as a function of velocity. The radius of the object is not needed for this calculation.
kevinf

## Homework Statement

Calculate the force required to pull a copper ball of radius 2.50 cm upward through a fluid at the constant speed 9.00 cm/s. Take the drag force to be proportional to the speed, with proportionality constant 0.950 kg/s. Ignore the buoyant force.
1 N

R=(1/2)DPAV^2

## The Attempt at a Solution

the above formula may not be correct but its something like that. i tried to use that formula to calculate the force but the problem doesn't give me all the information required to plug it into the formula. is there anything that i am missing taht you guys can guide me through

Draw a free body diagram of the ball. There are three forces acting on the ball since the bouyant force is ignored. Because it's moving at a constant speed, the net force has to be zero.

so one would be the force that we are finding out, there is also a weight force and drag force pointing down? would the equation on the OP be required?

There is a V^2 in your equation. Note, that for whatever reason, the drag used is set proportional to the velocity, rather than velocity squared. I would begin by finding drag as a function of velocity.

Last edited:
The upward force is what you are solving for. You know the two downward forces, gravity and drag. Set the upward force equal to the sum of the two downward forces. The radius of the object has nothing to do with this problem because you were given the drag coefficient.

## 1. How does the density of the liquid affect the movement of an object?

The density of the liquid plays a significant role in the movement of an object through it. If the object is less dense than the liquid, it will float and move with the flow of the liquid. If the object is more dense, it will sink and require more force to move through the liquid.

## 2. Does the shape of the object affect its movement through liquid?

Yes, the shape of an object can greatly impact its movement through liquid. Objects with a streamlined shape, such as a fish, will experience less resistance and can move more efficiently through liquid compared to objects with a bulkier shape.

## 3. How can the viscosity of a liquid affect the movement of an object?

The viscosity, or thickness, of a liquid can greatly affect the movement of an object through it. A more viscous liquid, such as honey, will require more force to move an object through it compared to a less viscous liquid, such as water.

## 4. Is the speed of the object the only factor that affects its movement through liquid?

No, there are several factors that can affect the movement of an object through liquid. These include the density and viscosity of the liquid, as well as the shape and size of the object. The speed of the object is just one component that contributes to its overall movement through liquid.

## 5. Can the temperature of the liquid impact the movement of an object?

Yes, the temperature of a liquid can affect the movement of an object through it. In general, liquids become less viscous at higher temperatures, making it easier for objects to move through them. However, extreme temperatures can also impact the density of the liquid and affect the object's movement.

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