Lesson+19+&+20

**﻿Advancememt in Physics @ Dwight Englewood** **Director: Elise Burns** **TA: Sebastian Loh**

__Objective:__ A small sports car hits a heavy truck in a collision. What factors determine the outcome for the passengers of the two vehicles? Which driver will sustain worse injuries? Why? The passengers in the small sports car will sustain more injuries because the small sports car is not as massive as the truck. The mass of the truck and the sports car would determine the outcome for the passengers, according to Newton's Second Law.

__Materials:__ List any materials used and draw a labeled diagram of your set-up (alternatively, include a snapshot or video).
 * 2 magnetic 0.5 kg carts
 * 3 0.5 kg weights
 * track

__Procedure:__


 * 1) Place a cart on the middle of the track with the spring to the right. On a piece of masking tape, label this the "Target cart." Place a second identical cart on the right end of the track. Mark this as the "Bullet cart".
 * 2) Push the bullet cart very gently towards the target cart so that they collide, with the spring between them.
 * 3) Repeat step 2 several times, giving the bullet cart a bigger push each time. Record your observations.
 * 4) Add 500-g to each cart and repeat the process. Record your observations and compare the results to the first set of collisions.
 * 5) Remove the mass from the target cart and repeat the above steps.
 * 6) Add the mass to the target cart and remove the mass from the bullet cart, and repeat.
 * 7) Get the "Mystery" cart from your teacher. Determine the relative mass of the cart by putting it through a sequence of collisions.

__Mystery Weight Box 1__**:** Based on the reactin of the two carts my group guessed that the weight was 1300 grams. The target cart continued with the same speed as the bullet cart when holding 1300 grams. From this observation my group was able to hypothesize that the mystery weight had to be very close to 1300 grams.

__Mystery Weight Box 2__: Based on the reactin of the two carts my group guessed that the weight was 620 grams. The target cart continued with the same speed as the bullet cart when holding 620 grams. From this observation my group was able to hypothesize that the mystery weight had to be very close to 620 grams.

__Questions:__
 * 1) What is a real-life collision that the collisions in this investigation could represent? A real-life collision that this investigation represents is a collision between a sports car and a diesel truck.
 * 2) How well did observing collisions enable you to compare the masses of the carts in the last step? Observing the collision enabled me to compare masses of the carts in the last step because i was able to compare the behaviors of the two collision varying in mass on the carts.
 * 3) What happened after the collision as the masses changed? After the masses changed the collision I got to observe how the object behaved, it gave me a qualitative idea so after i was able to guess a quantitative value for the mystery box.
 * 4) Define the term momentum. ﻿The //quantity// of motion in a moving object. THe mass multiplied by the velocity.
 * 5) Which object has greater momentum, a butterfly traveling at 16 km/h or an eagle traveling at the same speed? The eagle would have a greter momentum because even though they re traveling at the same speed the masses vary tremendously.
 * 6) How does the transfer of momentum occur? The transfer of momentum occurs when objects collide and their velocities change.
 * 7) Use momentum to describe what would happen if a skaterboarder was hit by a car. If a car hit a skateboarder then the velocity of both object would change and the skateboarder would violently increase velocity.

__Conclusion:__
 * 1) Based on the relative amounts of momentum, what is the outcome of a head-on collision between a heavy truck and a small sports car if both have the same speed? ﻿﻿In this collision te sports car would travel in the direction of the truck becuse the truck has a greater mass compared to the sports car and the veloities of the automotive would cancel out because they are the same.
 * 2) Explain at least 1 cause of experimental error. Be sure you describe a specific reason. The force at which the cart was exerted was not constant so that would change the results enough to have some error.
 * 3) How would you improve the results of this lab? (In other words, what would you change about the materials or procedure to eliminate or reduce the experimental error you describe above?) ﻿I would change the method used to accelelrate the cart

Classnotes
Power is rate of dissapation (usage) P = w/t P = w/t P = fd?t P = F * A avg unit is WATTS 1 horsepower = 746 WATTS Conservation of Momentum Momentum cannot be created or destroyed but can be transferred. Total momentum of a system remains constant, as long as the system is isolated ( ignore friction ).

Conservation of Momentum


Power is the rate at which you do work, the rate of energy is dissipation << class Momentum = m x v it is the quatitity of motion. 

 What is the law of momentum conservation? Momentum lost by 1 object is equal to the momentum gained by the other object.

Refraction: when a wave meets an object (goes through) and changes direction of its path.