One system for understanding conservation of energy is to take the energy of a s
ID: 1658577 • Letter: O
Question
One system for understanding conservation of energy is to take the energy of a system pre collision and compare it to the energy of the system post collision. One example of a collision is the “elastic” collision where the objects collide similar to billiard balls during a game of eight ball. To mimic this in the lab you will load one cart with “N” magnets pointing out and a second cart with the “N” magnets pointing toward the other cart. When the carts collide the magnets will repel and it will appear to be similar to billiard balls. The second cart should be located about halfway down the track, and should be placed at the same location for each trial.
The second system the students will study is the so called “inelastic” collision where instead of repelling off of each other, when the carts collide they will stick together and make a larger mass. This sort of collision can often be seen at the scene of a car accident where the two vehicles become mangled together after colliding.
For each of the systems the students will use the motion detector to determine the speed of the carts before and after collisions. The scales can be used to determine mass of the carts. The spring loaded launcher should be used, similar to that of the 1-D lab performed previously in the semester. Three trials of each collision should be ran to determine statistical averages for initial velocity and final velocity.
Questions:
1.During an inelastic collision what happens to the energy that is removed from the kinetic energy of the initial cart? That is if Kinetic energy is not conserved.
2. Suppose you add mass to the second cart before each collision. How do you think this would affect how energy is conserved in both the elastic and inelastic collision?
3.Explain how the parabolic trajectory of a projectile is another example of conservation of energy.
Explanation / Answer
1. As we know that during an inelastic colision, bodies often stick together. When two bodies moving at some velocities collide together, they lose their velocities to a greater magnitude. It means the energy is not conserved as it depends on the velocity. This energy may get converted to heat energy, may dissipate in the form of noise or may dissipate in deforming the object. As an example, in a high speed head-on collision of cars, most of the kinetic energy is converted to deformation. The more the velocity, higher will be the deformation. Some of this energy is converted to noise and heat energy. Sometimes, some of the kinetic energy is left in the system that both cars will skid over some distance before coming to a full stop.
2. If we are increasing the mass, the energy will also increase. In case of inelastic collison, if mass of one body is large, it will have higher energy. It means on collision, it is highly likely for object with bigger mass to impart more energy and to undergo less deformation. In case of elastic collison, energy remains conserved.
3. A projectile will have potential and kinetic energy. Notice that potential energy comes into picture when there is a gain in height and kinetic energy is due to its velocity. Initially, the projectile doesn't have any potential energy because it is at ground level this means mgh = 0 because h = 0 at ground. Therefore the only energy in action is kinetic. As the ball flies, the kinetic energy will change to potential enegy because heigh will increase and velocity will decrease. At highest point velocity is zero, therefore, K.E is also zero at highest point.
Therefore, Initial kinetic energy is equal to final potential energy. This proves conservation of energy that energy can neither be created not be destroyed but can be transformed from one form to another.
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