Is the Coefficient of Restitution Constant for All Collision Velocities

Crumple zones are designed to absorb the energy from the impact during a traffic collision by controlled deformation. This energy is much greater than is commonly realized. A 2,000 kg (4,409 lb) car travelling at 60 km/h (37 mph) (16.7 m/s), before crashing into a thick concrete wall, is subject to the same impact force as a front-down drop from a height of 14.2 m (47 ft) crashing on to a solid concrete surface. Increasing that speed by 50% to 90 km/h (56 mph) (25 m/s) compares to a fall from 32 m (105 ft) - an increase of 125%. This is because the stored kinetic energy (E) is given by E = (1/2) mass × speed squared. It increases by the square of the impact velocity.

The ball now has kinetic energy. Kinetic energy like momentum in that it comes from the mass of the object and its velocity. Kinetic energy was transferred from the plunger to the ball just like momentum was but only if the collision was elastic. During and elastic collision kinetic energy is conserved. The balls kinetic energy is half of its momentum squared. This means the balls momentum is its mass multiplied by velocity, and then it is squared and divided by two. If the velocity or speed of the ball is reduced by one half then the overall kinetic energy is reduced by a factor of four (Kirkpatrick and Wheeler p.106)

The energy absorbed by the fabric in the armor is equal to the loss of kinetic energy carried by the bullet during impact.

Write theories for each of your experiments performed here. They may not be the same as anyone else!

After viewing the trials of drops, multiple flaws were highlighted in many designs of the lab participants. One flaw that could have been improved on was more even distribution of straws surrounding the egg compartment, rather than overbuilding on one side. This could be solved by building symmetrically. Another noticeable flaw was the reckless flight patterns of designs

Hypothesis: No the size of the crater and ejecta will change because it will have lighter and harder impacts on the surface.

Hypothesis: I predict that the velocity of the stopper will increase as the radius is shortened.

An elastic collision is a collision in which kinetic energy is conserved, such as when a running back is hit so hard by the opposing team’s linebacker on a lead-draw play up the middle that the ball is forced out of his arms. The fumbled ball then hits the turf and because of the elasticity of the collision it bounces back up. Unlike an elastic collision, an inelastic collision does not conserve the kinetic energy of the colliding objects (Kirkpatrick & Wheeler 134). An example of an inelastic collision might be when a player catches the ball (if he catches the ball) and the momentum of the ball is completely stopped. However it is important to realize in this study of physics that a

The lab to which I have referred is the dropping coffee filters from a known height in order to investigate terminal velocity. Having spoken to local physics teachers both before and after my presentation to

Using the toy cars and track, the lab was conducted to prove that the momentum before a collision would be equal to the momentum after a collision. The most significant results that was produced by the experiment was that the momentum before the collision, being 0.05929 kg*m/s, and the momentum after, being 0.0682 kg*m/s, were not equal like they should have been. These results from the lab were not accurate in the fact that the before and after momentums were not the same, which helps to show that lab measurements will be slightly off due to inaccuracy of the lab equipment.

While determining which of the three collisions (stick together, magnetic and explosion) were most elastic and inelastic, we found that we were not going to find one-hundred percent conservation throughout this experiment. With respect to momentum, we found that all of our collisions conserve momentum relatively well, with our highest percent error of 22 percent on the Head-on stick together collision. Though we were unable to calculate a percent error on the explosion collision, we can accurately conclude that the head-on magnets collision had the best conservation of momentum as we had a percent efficiency of 91 percent. When observing conservation of energy in this experiment, we did not have nearly the same results as we did in the conservation of momentum. Once again the magnet head-on collision came out on top with being able to conserve the most, this time with respect to the collision that conserves the most energy.

It has been discovered that kinetic energy from a head collision can transfer to the brain in the form of kinetic and elastic energy which can cause serious brain damage through deformation (Moore, 2016). Sports helmets are specifically designed to dissipate as much energy from a collision before it reaches the brain. Also, the helmet prevents the impact from fracturing the skull, causing more serious damage. Engineers use the law of conservation of energy to design the helmets. The helmets dissipate the energy by transforming it into kinetic and elastic energy that doesn’t reach the brain (Moore, 2016). The energy is also transformed into sound and heat due to the friction from the contact. Engineers use the same concepts that I’ve learned in class about the law of conservation of energy which states that energy cannot be created nor destroyed, but it can only transform into different forms of energy. We’ve learned that the initial amount of energy is equal to the final amount of energy. According to this, the total kinetic energy from the collision is equal to the total energy at the end which consists of forms like elastic, thermal, kinetic, and sound energy. By splitting the total amount of energy into different forms of energy that are stored or directed away from the head, the amount of energy affecting the brain is much less (“Newton’s Cradle: Colliding football helmets : Physics 101”, 2012).

The law of conservation of momentum states that when two bodies collide with one another, the momentum before and after the collision is exactly the same if there are no external forces acting on the system. Although when there are external forces acting there will be a change in overall energy of the objects, as some of it may be lost to friction. Some of the energy is lost due to the deformation of objects caused by the collision. Hence during the time interval of the collision the velocities of these objects tend to change. By using the ratio of the velocities before and after the collision their elasticity can be calculated. This measure of elasticity is known as the coefficient of restitution. This coefficient is dependent on the material of the objects.

Several systematic occurred in this experiment, but the most important one would have been the fact that the air hockey table was not completely level. This impacted upon the experiment in two ways. In the first experiment where the red puck is initially stationary, as the table was not level it moved around before the black puck collided with it. To overcome this the red puck had to be held in place and as mentioned before this would have provided and external force acting upon the puck. The unevenness of the air hockey table also meant that there was a possibility of friction acting on the pucks while they were moving. In the third collision with the Velcro another systematic error occurred. When the two pucks collided and stuck together they did not continue straight, instead they rotated. This is not linear momentum but rather it is angular momentum. This is reflected in the results as the magnitude of the initial and final momentum of the system is equal, but the

P1 - How does it contradict the Law of Conservation of Mass and the Law of Conservation of Energy?