Acceleration in Water compared to Air

In summary, the approach for calculating the velocity and kinetic energy of an object dropped through a known height in water is similar to that used for air, but with the added factor of water resistance. The equations and approach are identical, but the resistance effects are more pronounced in water. Additionally, the buoyancy force must be taken into account. By vectorically adding the forces, the velocity can be calculated and then the kinetic energy can be determined.
  • #1
Rich M
1
0
If an object is dropped in air through a relatively short known height (say 2m) on earth, then ignoring any air resistance its velocity on impacting the ground can be calculated from standard laws of motion. Its kineteic energy at impact can then be calculated if its mass is known. My question is what would be the approach for calculating the velocity and/or kinteic energy for the same object dropped through the same height in water?
 
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  • #2
Hi there,

As a matter of fact, your object dropped into water will be subject to the same gravitational pull. The only difference is that water will resist the movement much more. But the equations are the same, with the added water resistance factor.

Ok for the simple theory behind it. Fact is that the resistance of air/water or any other medium cannot be considered constant, like we tend to do so in physics 101. The amount of friction developed by the surrounding material is dependant on the velocity of the object (dr/dt) and on a friction coefficient, which is not the same as [tex]\mu[/tex].
 
  • #3
Comparing acceleration in air by "ignoring air resistance" to acceleration in water seems kinda like a cheat. Both air and water are fluids and the equations and approach one would use to model the resistance due to air or water are identical. However, in water these resistance effects are simply a lot more pronounced.
 
  • #4
Need to add (subtact actually) buoyancy force. A ping pong ball will float.
 
  • #5
Rich M said:
If an object is dropped in air through a relatively short known height (say 2m) on earth, then ignoring any air resistance its velocity on impacting the ground can be calculated from standard laws of motion. Its kineteic energy at impact can then be calculated if its mass is known. My question is what would be the approach for calculating the velocity and/or kinteic energy for the same object dropped through the same height in water?

Adding the forces like vicous force , upthurst force , Gravitational force and any other force if present vectorically will help youfind the velocity , then the kinetic energy
 

FAQ: Acceleration in Water compared to Air

What is acceleration in water compared to air?

The acceleration in water is generally slower than in air due to the higher density of water. This means that objects will require more force to accelerate to the same speed in water compared to air.

Why does acceleration differ in water and air?

The difference in acceleration is due to the properties of the medium. Air is less dense and offers less resistance, allowing objects to accelerate faster. Water, on the other hand, is denser and has a higher viscosity, resulting in slower acceleration.

How does the shape of an object affect its acceleration in water compared to air?

The shape of an object can greatly impact its acceleration in water compared to air. Objects with a smaller surface area, such as a bullet, will experience less resistance and therefore accelerate faster in water. Conversely, objects with a larger surface area, such as a flat sheet, will experience more resistance and have a slower acceleration in water.

Does the temperature of the water or air affect acceleration?

Yes, temperature can affect the acceleration of an object in both water and air. In water, colder temperatures result in higher density and therefore slower acceleration. In air, colder temperatures result in higher air pressure, which can also affect an object's acceleration.

How can we measure acceleration in water compared to air?

Acceleration can be measured using a variety of methods, such as using a stopwatch and measuring the time it takes for an object to accelerate to a certain speed. In water, buoyancy can also be taken into account as it can affect an object's acceleration. Additionally, specialized equipment such as accelerometers can be used to measure acceleration in both water and air.

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