I am currently doing a physics project where I am launching a wooden pellet by using a sling into a container full of water. By changing the length the rubber band is stretched, I am measuring the pellet's submergence distance into water.
I know that the velocity of the pellet must increase as the rubber band is stretched to greater distances, but I was wondering if air friction increases as well due to the increase in velocity?
I know friction increases in water when velocity is increased, so will that be relevant to my experiment as well?
What about some of the physics concepts related to my experiment? There is energy transfer from the rubber band to the pellet, and a reaction force from the water as the pellet hits it? Anything else?
Thanks in advance for helping!!
Call the spring constant of your rubber band k (in Newtons/meter for example).
Then the potential energy stored in the stretching is (1/2) k x^2 where x is the distance you stretch it.
When you release, most of that stored potential energy is released to your missile as kinetic energy (1/2)m v^2 where m is the mass in likograms and v is the velocity. Some energy goes into the motion of the band but we assume that the mass of the band is small compared to your missile mass so most goes into the missile.
There is air drag approximately proportional to size and fluid density and velocity squared times a form factor which is small for a streamlined missile and large for a spherical one.
When it hits the water, several things happen:
The water gets accelerated out of the way as the missile hits the water, which requires a de-accelerating force on your missile.
The drag force goes way up because although the missile size and form factor are the same as in air, the density of water is about 800 times as much so the drag is much greater and it will slow down more.
By the way, although most missles are streamlined as I suggested, the problem is that they tend to turn sideways and need fins on the back to go straight, which is why you see fins on arrows and bombs and such. Another way to make a missle go straight is to spin it along the axis of flight, which is how a rifle works wit a spral ridge to spin the bullet as it travels down the barrel.
Hope these few hints help.
In your physics project, you are investigating the submergence distance of a wooden pellet launched into a container of water using a sling. You have a few different questions related to the physics concepts involved, so let's address each one.
1. Does air friction increase as the rubber band is stretched and the pellet's velocity increases?
Air friction, or air resistance, does indeed increase as the velocity of an object moving through air increases. As you stretch the rubber band further, the pellet will be launched with a higher initial velocity. This increased velocity will lead to a greater amount of air resistance acting on the pellet, potentially affecting its trajectory and submergence distance in the water. It's important to keep in mind that the effect of air resistance may be relatively small compared to other factors involved in your experiment, such as water resistance.
2. Does water resistance affect the submergence distance?
Yes, water resistance plays a role in your experiment. When the pellet enters the water, it experiences resistance, known as drag or water resistance, due to the interaction between its motion and the water molecules. As the velocity of the pellet increases, so does the water resistance. This increased resistance can potentially limit the submergence distance of the pellet.
3. What other physics concepts are relevant to your experiment?
a. Energy transfer: When you stretch the rubber band, you are storing potential energy in it. As you release the sling, the potential energy is converted into kinetic energy, propelling the pellet forward. The kinetic energy of the pellet determines its velocity, which in turn affects the submergence distance.
b. Reaction force: When the pellet hits the water, it experiences a reaction force from the water. This force acts against the motion of the pellet, potentially reducing its velocity and influencing the submergence distance.
c. Trajectory: The path followed by the pellet while traveling through the air and water is known as its trajectory. The trajectory can be influenced by various factors, including initial velocity, angle of launch, air resistance, and water resistance.
It's worth noting that in order to accurately predict and analyze the impact of air and water resistance on your experiment, you may need to consider additional variables and conduct more detailed calculations, such as taking measurements of drag coefficients and drag forces.